alright, well due to you posting in the new owners section, you probably arent going to get the attention you need, but have faith... your issues are not as bad as you think.
in this order, you need to do stuff to get the car running correctly, and you can go from there.
this is a good resource for some information
Main Page - 3SI Wiki
so is the website "stealth316.com"
1. get a stock ECU. the codes were just posted above, and from memory, i believe they are correct. there are no drop in stand alone ecu's... this is a niche platform. dont use the same mindset you use with ANY other platform. it wont work haha
2. fix the fuel pump. i say fix, because it sounds like its dying, you dont know whats really in there, and its not hard to take out so its really no big deal. there is a plate with the fuel pump tophat and like 6 bolts under the spare tire in the rear. a new fuel pump is like $100 so worse comes to worse, its not even that much money
3. fix the vacuum lines. Vacuum Reduction - 3SI Wiki
you can also search on here for other vac reduction links. you dont 'need' any vac lines except the ones that run to the wastegates (and brake booster but im talking about lines, not the big hoses). depends on how 'stock' you wanna make it.
those are honestly your biggest issues. with the parts in front of you, all of those wouldnt take but 4 or 5 hours to fix.
now when i say everything, i am just taking what you say and going with it. there could be a lot of underlying issues that you dont even know about. like you said it lost spark, so you need to test the coils: Stealth 316 - Ignition Coils
i think you should take out the fuel pressure regulator and put in a stock one. along with stock injectors.
those first 3 are the big ones though. after that, you should be able to start narrowing down the issues. the ecu is the biggest one. make sure the ecu you get does NOT HAVE LEAKING CAPACITORS. if it does, replace them (im pretty sure there are 2 that are notorious for leaking).
thats all i can think of, but there isnt really that much to do, you will be fine. and it wont be that much money for all the parts. just get used stuff that is known working correctly.