Hey, Awesome build. Wish I had your mechanical skills...would save so much money on my internal work....
I'm getting the leather seats for sure now.
As far as the exhaust goes, I got a 3" divorced downpipe, into RT Cat, and the HKS turbo exhaust. Mine had the same problem to begin with. Just before the downpipe gets to the cat, there is a bracket that the oem exhaust bolts directly to and does not use hangers. There, you can fabricate an exhaust bracket to or just use a hose clam as I did (see picture).
Also, with the hangers on the very back near the pipe, i doubled up on the left (drivers) side to make the pipe even more level (with tighter hangers) and it was a b*t(h to get on there, but they are almost level (picture). I hope this helps.