Bruising, swelling, and blistering all require a BP string of some sort to tell them what body part and tissue to apply it to. You can use :LOCALIZED:VASCULAR_ONLY and it will affect tissues with blood vessels on body parts the spit lands on.
Pain can also accept BP tokens but it's not a requirement, apparently.
Keep in mind that heavy swelling will result in tissue necrosis. I would suggest keeping the swelling severity low, or your "not very effective" syndrome will have a near-100% fatality rate unless the tissue is surgically excised by a doctor.
The timing definitely isn't the issue; your timing strings are correct in both examples you posted. 9000 time units is about 4.5 days in dwarf mode, you can use DWF_STRETCH:x to multiply that timeframe if its too short. One issue might be the PEAK value; the syndrome builds up to that point and then lessens afterwards, so it could be everyone is passing out at around 200 and then by the time 3000 comes around they're barely feeling it anymore because it's fading away. Could put the peak value closer to the end value, and then it will build up over a longer period and rapidly subside.
Could a material emission be used to harmlessly drop the fruit or would that hurt people?
Maybe. Although you could use [LAYS_UNUSUAL_EGGS] instead.
But what do I know?
item-cloud material emissions will produce pools of items laying on the ground, but I'm not sure dwarves can even pick up those items. Maybe if they're dropped in a fruit/plant gathering zone and an herbalist gets to them? Dunno. Otherwise, your dwarves will try to clean up the pools as if they're a blood spill.
You can have it periodically (say every full moon) transform into another caste of the creature which has two excess body parts; one connected to the body which has only one tissue layer which is made out of a substance that is gaseous at room temperature and thus boils, and the second connected to the first and made out of the "fruit" you desire and a skin (or muscle... whatever) covering it, which will fall off when the first boils away. Your dwarves will haul that second body part to a refuse stockpile as a discarded body part, and if the creature isn't intelligent will then butcher it; yielding the "fruit" and a skin. This takes about 800 ticks in fort mode for most body parts to boil away, so a transformation that lasts for 1000 ticks should give enough time.
It needs a skin layer, or at least some other tissue layer, because the game doesn't like single-tissue body parts being butchered. If there are two or more tissue layers then they can butcher it.