Hi George & Mrs George! Welcome to the forum. As you surmised, you're going to get a lot of comments on your camper-truck matchup. Most folks here are trying to be helpful. You said this is your first RV so you're at the bottom of a steep learning curve. Your comment that your first night was MISERABLE hints of a few steps you've already taken up the learning curve :E You'll have to share that story some time :B
The 815 is designed for an 8' bed truck and needs support along its full length for its structure and the heavy water and waste tanks enclosed. Your tailgate may not be strong enough to provide the support it needs. It may hold for a while but the inevitable bumps along the road will stress the tailgate, the camper, or both. One option you might consider until you can switch to a long bed truck is to put the camper on a trailer and tow it behind the truck. Yeah, that defeats part of the purpose of having a truck camper, but it would eliminate the support issue and other concerns that your camper-truck matchup raise. And it would even help solve your problem with the steep terrain at your home as you wouldn't need to unload it. You can find some previous posts where others have done this and it works out really well, sometimes even providing extra room to store gear or to serve as a porch.
Oh, and Happy Anniversary!