You have to be careful about carrying around a lot of cash. You get stopped by the police and they find it they may sieze it and you play hell getting it back. Civil Asset Forfeiture is what it is called. Saw some legal videos online about it and it looks like a quagmire if it happens to you.
The measurements depend on the coupler face size. For example if the coupler is 6” then the alignment should be within .006” all around the coupler. .001 per inch of coupler face.
The price for the rebuild may be a bit high but not out of the ball park.
As to supporting the shaft it would depend on the particular shaft and how it is supported by the shaft log and cutlass bearings.
The engine should be realigned after this work. Not sure what you mean about 8” move.
What thread are you using? If you are in a sunny climate then Poly thread won’t last long. I only use Tenara thread. Sailrite has a similar thread also. It is very slippery so the tensions on the machine has to be adjusted. But it will last forever.