Sometimes you can manage to get the bolt out the top. I think that the variable is the condition of the motor mount. If the motor mount on that side is sagged, then it's just enough to limit the access.

I say that, but I think I even tried raising the engine before and still didn't have enough clearance. Of course you should try first to get the bolt out the top, if for no other reason to keep from having to cut it.

As far as how tight for the idler arm bolt? Tighten until there is no slack. You will have to push hard on the idler arm to feel the slack. It may very well take a 1/2" impact wrench to get it tight enough.

Good luck,