Leave it on the transmsion. Just unplug the vacuum line. For a period of time I had a M200 tranny in my Buick (which does not use a vacuum operated modulator) and I removed the vacuum line and capped it off where it connected to the intake manifold.
On my Buick the vacuum line was a piece of aluminum tubing that was connected via a 2 inch section of rubber vacuum hose that had hardened with age. It took some work, but I did pull it off. If need be you can just slice through it with a razor blade.
I typically use a wrench on my upper bellhousing bolts. Of course since I tightened them myself, I know they are not over-tightened...
If you have the box end squarely and completely over the bolt head, you can tap the wrench with a hammer or "double up" on the wrenches (i.e. attach the box end of one wrench to the open end of the other wrench) and increase your leverage.
All of my vacuum hoses just slide off & on, sorry I can't help with that. But you may have to be more careful with your adjustment hardware for your downshift cable, if so equipped. A misadjustment on that can ruin your transmission (as I'm sure you are aware).
I always use 4 or 5 extensions and a swivel socket while laying back around the tailshaft... I've only done transmission work on F-Body's though. Years from '82-'02 just had ZERO room to get anything on the top of the bellhousing from above. The only way I know how to do them is with 3' of extensions and a universal/swivel socket. Snap-On or S&K I don't remember, but one of them makes some 360* ones that don't bind up... a friend let me use them last time I did a clutch on my Z28. It made the job a lot easier.