You simply have to move it out of the main part of the creature, and secure it within a caste definition. What I've done below is select the spawner and the androspawner using the select caste and select additional caste tags, and gave them their body and materials. Then I made a select caste tag select every caste to apply things such as blood, as well as things that require the body parts and materials to be defined first first, such as attacks.
The venom should be fine where it is, unless it is used as a material for a body part.
creature_custom
[OBJECT:CREATURE]
[CREATURE:KIZAUR]
[DESCRIPTION:A basilinian humanoid of large stature and aggressive nature]
[NAME:Bazlin'kizaur:Kizaur:Kizaurun]
[CASTE_NAME:bazlin'kizaur:kizaur:kizaurun]
[INTELLIGENT]
[CANOPENDOORS]
[BENIGN]
[TRANCES]
[PREFSTRING:Burning glands]
[PREFSTRING:sleek scales]
[USE_MATERIAL_TEMPLATE:VENOM:CREATURE_EXTRACT_TEMPLATE]
[STATE_NAME:ALL_SOLID:frozen bazlin venom]
[STATE_ADJ:ALL_SOLID:frozen adder venom]
[STATE_NAME:LIQUID:bazlin venom]
[STATE_ADJ:LIQUID:bazlin venom]
[STATE_NAME:GAS:boiling bazlin venom]
[STATE_ADJ:GAS:boiling bazlin venom]
[PREFIX:NONE]
[ENTERS_BLOOD]
[SYNDROME]
[SYN_NAME:bazlin tarsal injection]
[SYN_AFFECTED_CLASS:GENERAL_POISON]
[SYN_IMMUNE_CREATURE:ADDER:ALL]
[SYN_INJECTED]
[CE_PAIN:SEV:75:PROB:100:RESISTABLE:LOCALIZED:VASCULAR_ONLY:START:7:PEAK:50:END:900]
[CE_SWELLING:SEV:15:PROB:85:RESISTABLE:SIZE_DILUTES:LOCALIZED:VASCULAR_ONLY:START:5:PEAK:900:END:1500]
[CE_BLISTERS:SEV:40:PROB:90:RESISTABLE:SIZE_DILUTES:LOCALIZED:VASCULAR_ONLY:START:20:PEAK:750:END:1300]
[CE_NUMBNESS:SEV:90:PROB:100:RESISTABLE:SIZE_DILUTES:LOCALIZED:VASCULAR_ONLY:START:1:PEAK:10:END:3250]
[CE_DIZZINESS:SEV:100:PROB:100:RESISTABLE:VASCULAR_ONLY:START:1:PEAK:10:END:4500]
[BODY_SIZE:0:0:8000]
[BODY_SIZE:6:168:40500]
[BODY_SIZE:23:0:95000]
[MAXAGE:60:120]
[BABY:1]
[CHILD:23]
[EQUIPS]
[CREPUSCULAR]
[HOMEOTHERM:10067]
[SWIMS_LEARNED][SWIM_SPEED:1500]
[MANNERISM_LAUGH]
[MANNERISM_SMILE]
[MANNERISM_WALK]
[MANNERISM_SIT]
[MANNERISM_BREATH]
[MANNERISM_POSTURE]
[MANNERISM_STRETCH]
[MUNDANE]
[PHYS_ATT_RANGE:STRENGTH:500:1000:1200:1600:2000:2550:3250]
[PHYS_ATT_RANGE:AGILITY:650:1200:1800:2050:2700:3300:3800]
[PHYS_ATT_RANGE:RECUPERATION:650:1200:1800:2050:2700:3300:3800]
[PHYS_ATT_RANGE:DISEASE_RESISTANCE:650:1200:1800:2050:2700:3300:3800]
[PHYS_ATT_RANGE:TOUGHNESS:550:1050:1300:1450:1650:1900:2450]
[PHYS_ATT_RANGE:ENDURANCE:500:1000:1250:1350:1550:1800:2300]
[MENT_ATT_RANGE:ANALYTICAL_ABILITY:550:1000:1200:1500:1900:2300:2750]
[MENT_ATT_RANGE:FOCUS:700:1200:1600:2000:2200:2800:3500]
[MENT_ATT_RANGE:CREATIVITY:900:1600:2100:2775:3350:4000:4850]
[MENT_ATT_RANGE:PATIENCE:400:900:1150:1250:1400:1800:3000]
[MENT_ATT_RANGE:MEMORY:450:950:1150:1250:1350:1550:2250]
[MENT_ATT_RANGE:WILLPOWER:650:1050:1350:1550:1800:2150:2750]
[MENT_ATT_RANGE:SPATIAL_SENSE:780:1400:1800:2100:2500:2900:3500]
[MENT_ATT_RANGE:KINESTHETIC_SENSE:800:1420:1830:2140:2560:2980:3600]
[MENT_ATT_RANGE:INTUITION:800:1400:1800:2100:2500:2900:3500]
[PERSONALITY:ACTIVITY_LEVEL:20:75:100]
[PERSONALITY:CAUTIOUSNESS:0:35:95]
[PERSONALITY:ACHIEVEMENT_STRIVING:45:85:100]
[PERSONALITY:SELF_DISCIPLINE:15:55:100]
[PERSONALITY:DUTIFULNESS:15:60:100]
[PERSONALITY:ORDERLINESS:30:55:100]
[PERSONALITY:SELF_EFFICACY:20:75:100]
[PERSONALITY:SYMPATHY:0:45:100]
[PERSONALITY:MODESTY:0:20:50]
[PERSONALITY:COOPERATION:0:35:60]
[PERSONALITY:ALTRUISM:10:55:100]
[PERSONALITY:STRAIGHTFORWARDNESS:5:60:100]
[PERSONALITY:TRUST:0:45:100]
[PERSONALITY:LIBERALISM:35:75:100]
[PERSONALITY:INTELLECTUAL_CURIOSITY:35:80:100]
[PERSONALITY:ADVENTUROUSNESS:15:75:100]
[PERSONALITY:EMOTIONALITY:0:65:100]
[PERSONALITY:ARTISTIC_INTEREST:10:55:100]
[PERSONALITY:IMAGINATION:15:65:100]
[PERSONALITY:CHEERFULNESS:10:45:100]
[PERSONALITY:EXCITEMENT_SEEKING:35:85:100]
[PERSONALITY:ASSERTIVENESS:40:85:100]
[PERSONALITY:GREGARIOUSNESS:5:50:95]
[PERSONALITY:FRIENDLINESS:0:65:100]
[PERSONALITY:VULNERABILITY:0:20:65]
[PERSONALITY:IMMODERATION:0:52:85]
[PERSONALITY:SELF_CONSCIOUSNESS:0:15:25]
[PERSONALITY:DEPRESSION:0:60:90]
[PERSONALITY:ANGER:30:87:100]
[LITTERSIZE:10:15]
[CREATURE_TILE:'f']
[COLOR:7:0:1]
[EXTRAVISION]
[CASTE:KIZAUR]
[CASTE_NAME:Bazlin'kizaur:Kizaurun:Kizaur]
[POP_RATIO:100]
[CASTE:SPAWNER]
[FEMALE]
[CASTE_NAME:Bazlin'kizaur:Kizaurun:Kizaur] [POP_RATIO:15]
[CASTE:ANDROSPAWNER]
[MALE]
[CASTE_NAME:Bazlin'kizaur:Kizaurun:Kizaur] [POP_RATIO:15]
[SELECT_CASTE:KIZAUR]
[SELECT_ADDITIONAL_CASTE:SPAWNER]
[SELECT_ADDITIONAL_CASTE:ANDROSPAWNER]
[BODY:SPINED_HUMANOID_CHEST:SPINED_HUMANOID_RIGHT_ARM:SPINED_HUMANOID_LEFT_ARM:SPINED_HUMANOID_RIGHT_LEG:SPINED_HUMANOID_LEFT_LEG:SPINED_HEAD:SPINED_HUMANOID_INTERNAL]
[BODY_DETAIL_PLAN:KIZAURUN_DEFAULT]
[BODY_DETAIL_PLAN:BAZLIN_TISSUES]
[BODY_DETAIL_PLAN:BAZLIN_MATERIALS]
[CASTE:WRAITH]
[CASTE_NAME:kizaur wraith:kizaurun wraiths:kizaur][POP_RATIO:1]
[BODY:SPINED_HUMANOID_CHEST:SPINED_HUMANOID_RIGHT_ARM:SPINED_HUMANOID_LEFT_ARM:SPINED_HUMANOID_RIGHT_LEG:SPINED_HUMANOID_LEFT_LEG:SPINED_HEAD:SPINED_HUMANOID_INTERNAL:LEFT_TARSAL:RIGHT_TARSAL:SPINED_TAIL:SPINES]
[BODY_DETAIL_PLAN:KIZAURUN_CHOSEN]
[BODY_DETAIL_PLAN:BAZLIN_TISSUES]
[BODY_DETAIL_PLAN:BAZLIN_MATERIALS]
[CASTE:LEGIONNAIRE]
[CASTE_NAME:Kizaur legionnaire:kizaur legionnaires:kizaur][POP_RATIO:3]
[BODY:SPINED_HUMANOID_CHEST:SPINED_HUMANOID_RIGHT_ARM:SPINED_HUMANOID_LEFT_ARM:SPINED_HUMANOID_RIGHT_LEG:SPINED_HUMANOID_LEFT_LEG:SPINED_HEAD:SPINED_HUMANOID_INTERNAL:LEFT_TARSAL:RIGHT_TARSAL:SPINED_TAIL:SPINES]
[BODY_DETAIL_PLAN:KIZAURUN_WARRIOR]
[BODY_DETAIL_PLAN:BAZLIN_TISSUES]
[BODY_DETAIL_PLAN:BAZLIN_MATERIALS]
[SELECT_CASTE:ALL]
[USE_MATERIAL_TEMPLATE:SINEW:SINEW_TEMPLATE]
[TENDONS:LOCAL_CREATURE_MAT:SINEW:200]
[LIGAMENTS:LOCAL_CREATURE_MAT:SINEW:200]
[HAS_NERVES]
[USE_MATERIAL_TEMPLATE:BLOOD:CIDAELA_TEMPLATE]
[BLOOD:LOCAL_CREATURE_MAT:BLOOD:LIQUID]
[ATTACK:KICK:BODYPART:BY_TYPE:STANCE]
[ATTACK_SKILL:STANCE_STRIKE]
[ATTACK_VERB:kick:kicks]
[ATTACK_CONTACT_PERC:100]
[ATTACK_FLAG_WITH]
[ATTACK_PRIORITY:SECOND]
[ATTACK:BITE:BODYPART:BY_TOKEN:SNOUT]
[ATTACK_SKILL:BITE]
[ATTACK_VERB:bite:bites]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PENETRATION_PERC:100]
[ATTACK_FLAG_EDGE]
[ATTACK_PRIORITY:MAIN]
[ATTACK_FLAG_CANLATCH]
[SPECIALATTACK_INJECT_EXTRACT:LOCAL_CREATURE_MAT:VENOM:LIQUID:100:100]
[ATTACK:DRAIN:BODYPART:BY_TOKEN:SNOUT]
[ATTACK_SKILL:BITE]
[ATTACK_VERB:drain:drains]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PENETRATION_PERC:100]
[ATTACK_FLAG_EDGE]
[ATTACK_PRIORITY:MAIN]
[ATTACK_FLAG_CANLATCH]
[SPECIALATTACK_SUCK_BLOOD:20:50]
[ATTACK:TARSAL_JAB:BODYPART:BY_CATEGORY:TARSALEND]
[ATTACK_SKILL:GRASP_STRIKE]
[ATTACK_VERB:tarsal jab:jabs with tarsal]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PENETRATION_PERC:100]
[ATTACK_FLAG_EDGE]
[ATTACK_PRIORITY:MAIN]
[ATTACK_FLAG_CANLATCH]
[SPECIALATTACK_INJECT_EXTRACT:LOCAL_CREATURE_MAT:VENOM:LIQUID:100:100]
Alternatively, you could leave the main body as a base, and remove the duplicated parts from the castes. Though you would still need to move the tissue detail plans at least, to avoid overlap.