Florida man, others have given you lots of good advice. I'm going to second the person wh suggested you talk to the hospice staff about her pain level. You could also ask if her moaning is from pain. It could have another cause.
Please allow yourself to get some sleep. You can't go without sleep indefinitely. It6not going to help you or your wife. When my mom was dying I dozed in a chair next to her bed holding her hand. I got some rest, but we were still connected.
You asked how to cope with the grief of losing someone before they die. Best thing I know is to let yourself grieve in the way that works for you. Let yourself feel whatever emotions come up. Don't be surprised if you have a sense of relief after she passes. It's not uncommon.
Lastly, it's good to let her know it's okay to go. Sounds odd, but some times people hang on because they believe their loved ones want them to stay.
I'd encourage you to continue to post here for support. The folks at PC are great. Another fantastic resource that helped me after my husband died was widownet.org