Fun Tips:
1. Perk:
Slow and Purposeful - Really does boost your defense. It is MUCH harder to get units killed for geneseed, cause you got a much higher chance of things going to hell by the time you do take casualties over the medic healing limit. (Also, it seems your medics are more likely to get hurt first rather then the marines.)
1a-On that note, with this perk, if you bring everything down on a Necron infested planet... you basically have an extended training ground with very light-no casualties if you bring all your medics. (Vehicles tend to be the ones that die first...) You could also survive against an ork invasion numbering less then 10k without too many problems.... well, there is the issue of attack power.
1b. The lack of casualties.... now that I compare. The buff to defense is pretty broken. Just the side effect of it being much harder to acquire geneseed...
2. For some odd reason, Inquisitor disposition drops 10 points when your max chapter size is between 6, 7 and 8.
2a. Inquisitors like for you to have pure genes.
3. Being doomed might not be too bad with slow and purposeful and you don't get in over your head. You could last awhile without any casualties. (Not like you'll be gaining much geneseed anyways.
3a. You could probably spend you geneseed on mechanic troops from the start at a pretty good rate it looks like...
Skitarii, something like 10 for 5 genes
4. 5 points in max chapter size gives you the normal starting amount of marines. (990-some) Less points = starting with less troops. Theoretically, you don't really have much room to grow...
5. If you want to cheese it, choose unimplemented negative perks for more points.
6. 10 gene stability is not 100% stability apparently, maybe 99% or something.
EDIT: Also, screenshot the map. It helps for inquisitor quests.
And... what is with Librarians? Do they do Psyker stuff?