Adding the additional hanger might not be much help if the downpipe is a touch long and just hangs lower. However, if the exhaust is just being held up by the downpipe flange bolts and the muffler hanger, you probably should add one for extra support.
You might be able to loosen the downpipe and separate the rest of the exhaust from the downpipe. Then put the DP where you want it to be (raise end up, etc) and support/secure it in place while you tighten the DP back down at the turbo. If you don't have an extra set of hands, use something as a spacer between the DP and the x-member and hold it in place with a bungy cord or something. Just an idea. The end of the DP looks slightly angled down in the second pic, so some adjustment may be needed to get things higher.
Looks like the main problem is that it's low up front. You could go up at least another inch and tuck it up tighter to the transmission X-member.Then you could make the whole thing tighter to the floorpan all the way back to the muffler, and bring it up too.
Perhaps it was different in my 2.3T swap, but it was also EEC IV and I don't remember any odd shenanigans with the dash harness. Sure there are connections to be made for idiot lights, etc, but nothing too deep.
It was however almost 20 years ago when I did it, and my notes are kind of spotty, but the non-2.3T dashes in the '83-'84 cars are pretty basic.
Whatever harness you start with, you'll just need to pare it down to what you need.
I used an old factory harness when I did the original 2.3T swap, but built a new one when I did the MegaSquirt install later.
If budget allows, a new, fresh harness is nice, but sometimes you have to work with what you have.
Unlikely that it, or anything, will just "plug in".
My car ('83) was originally a 5.0/auto. I manual swapped it and kept the EECIII for a while. Later I 2.3T/T5 swapped it, using stock EFI stuff. I used a harness from an 85 or 86 TBird, I think. I don't remember. It was almost 20 years ago when I did it. It however, did not just plug and play. It's got a MegaSquirt in it now, which has been in the car for a while now.
There isn't going to be much on the "chassis" side that you're going to need. You need to sort out a couple main power wires, but most of the main stuff will be there, seeing as the car was already EFI with electric fuel pumps. You're just going to have to grab wiring diagrams and compare to see what's what.