As far as #2 and the rest goes, I agree that with enough money you could make anything happen. However, sometimes recreating something so complex could be a "not enough money in the world" type situation. Sure, drawings and specs exist, but even on today's 3-d modelled assembly you're not typically modelling every single part to full accuracy. You have things that are off the shelf that might be a black box drop in, you have things you contract out that are built to spec. You know what you get, but not necessarily exactly how it's done. Then in your own facility there is a certain level of institutional knowledge that is not necessarily documented in such a way you can just recreate it.
Finally, one of the biggest hurdles, there's are not things that you can just throw an LLM and some engineers at. The actual trades themselves have changed so much since the time of production your only option is to call in retirees. The machinery is different now and so are the workers.
I feel like with a large budget they could definitely get an SR-71 in the air for testing and exhibition purposes, Id love to see it happen. I guess it really depends on how much was removed and destroyed when the machine was decomissioned and how much damage lack of maintenance, environmental factors and age have taken their toll. The good news is it hasn't been operated in a long long time. The bad news is it hasn't been operated in a long long time.
Source: I am a toolroom machinist at a material science lab in the aerospace and defense sector.