I don't hate you because your FPR isn't properly mounted. I promise though, you will hate you when your car catches on fire. Just sayin...
For the oil press sender, it's for the idiot light since out car's don't have an actual gauge. It's not a huge deal if it's not hooked up. Typically, by the time the light comes on it's too late. It is good for initial startup though. It's a great way to tell if you get oil pressure right away after a few cranks.
Even with a shorter oil filter, it still looks really close to the downpipe. I'd see if there was some way to shield it from the heat. You could wrap the downpipe with exhaust wrap. Or, you could even fab up a small heat shield.
You're making progress on the car, and that's what matters. Sometimes it's overwhelming when all the little stuff adds up though. Don't let that stuff discourage you.