I am pretty sure I recommended a different order of assembly in a previous thread, starting with the seat tube, then the ht/dt, then the front triangle. That's a traditional building technique for a reason. Individual joints always seem to settle out at an angle that aren't what you wanted. Bottom brackets in particular have a way of moving that I don't want to have to predict, so I like to have everything else nailed down first.

I assume this bike is for Brandon. Since this is the bad advice forum, I would spring the tube out and finish the build. I really think the effects of that are overblown. Make sure the miters still fit, this is why bikes that have been sprung fail. Reheating is not a good idea. When I reheat a tube, it's going to metal recycling. BB shells and lugs can be reused if disassembled with care.

Am I reading it wrong that all that is bad is a bb shell and a downtube? In that case, just replace them. Throwing stuff out is good for the soul and good practice moving forward. Don't keep it around, that is just bad energy you don't need. I had a fork I didn't feel good about and didn't want to use that I carried around for 36 years. Finally cut it open and found out that it was perfectly fine to use. I wish I had done that 36 years prior.