I mean it looks sick even with the short comings! If that paint isn't Alumaluster you would have fooled me. It looks like Alumaluster to me, though I've never seen the stuff in person.
If you ask me, I would say the chest plate in completely salvageable. Cover the missing shiny spot with dirt and weathering. It wont look out of place if you weather the rest of the armour. It may not be 100% screen accurate but it would still look right. As for the pieces that don't quite fit together, I don't see a problem there. I'm making 3D printed armour right now and I'll be lucky if my pieces line up half as good as yours. If you think it is a problem you could always sand in back a bit.
Bucket size looks fine to me. Remember you'll be a bit bulkier with all the armour on. It might look big now but I'm sure with the rest of the suit it'll be great. I hope the suit works out for you! I'll be following this thread for sure.
