You may have noticed that some of the things you typed didn't show - so welcome to the board and review the rules you signed off on when signing up!
Thanks for adopting a shelter dog - a 6 year old to boot!
8-5 (not sure if those are work hours or if travel time is also in there) can be a long time for a dog without a break - I am wondering if you are able to come home at lunch, have a trusted/dog savvy person to help, or hire a walker/sitter 1x a day. The crate may make the anxiety worse - I would test it out a bit first.
For the poop, take what he does outside and let him see where you want him to go. Keep putting the poop out. Just calmly - no big deal, and start to reward him for pooping outside - you will need to fade that over time, but for now, things are new, so he needs to know what is good in order to do it.
Good that he's not urinating!
I would board a dog in a trusted facility rather than go to a situation of emergency with a new dog and 3 other dogs, as a new dog owner.