I'm not an expert at anything other than shotgun and I only played it once but I can answer a couple of those questions
For your psi needs Eidein made a good guide, it's a little outdated but still works
https://stygiansoftware.com/forums/index.php?topic=8972.0Metal armor and Psi don't really gel together because there are much better armors that give amazing bonuses, like a Tac Vest made with the shell of a psi beetle decreasing psi cost and increasing psi skill, or other unique armor giving all kinds of bonuses. You also won't have many stat points to invest in Str to wear it so I don't recommend it.
If you really want to try Metal armor I'd say look at weapons thay already need Str and put more points in it, like shotgun, Assault rifle, grenade launcher, LMGs and Miniguns. I don't recommend playing a metal armor melee, ranged weapons can get away with it because they don't have to move to every enemy to actually do damage.
The only armor related feat that I have experience is Juggernaut which is very good, armor sloping is weird as it goes directly against making juggernaut work but I vaguely remember some combination or armor plates that makes juggernaut work and still have good defences and low armor penalty so you have a couple of MP.
Having thicc skull is actually worse than not having it, there are a couple of enemies that can stun you and are a threat when they do but if you're full metal armor with lots of health you should be able to survive the stun(with good positioning so you dom't get surrounded) and be immune to other stuns for a couple of turns. With thicc skull you'll be dazed instead which lowers your AP and depending on the weapon your damage lowers significantly, so surviving the stun and being able to act afterwards is preferred. And Bullhead also exists if you want to avoid stuns anyway.
Crafting is always good, especially for those items that you can't get otherwise. You can finish the game with only unique gear but I wouldn't recommend it for your first run as you would need to know where to find the items and build around them.
Armor penalty lowering dodge/evasion makes the two basically mutually exclusive, higher level enemies hit more often because they compare their weapon skill agaisnt your dodge/evasion which ia going to be higher.
Conditioning is good with high Con, I'm guessing you're talking about Force user? Is yes it is good for that Psi school, body weight training looks to me like a meme, 10% won't make that much of a difference.
Tranquility and psychosis completelt change the way you play, both have their pro and cons but I'm not an expert, but I know that each pairs better with different Psi schools, the guide by Eidein is good for that.
Health hypos and bandages are all you get at lower levels, later on you get better hypos and the option to use a Regen vest when crafting a Tac Vest and 1 regen drug but that's it.
My recommendation first of all is to read that guide, don't use metal armor with Psi, I'm guessing that you're maxing all 4 schools which can work but I don't recommend since you're limited by innervation slots, focus on 2 schools like the many examples in the guide