Well it sounds like a TT with opposing slides would work the best for you. It would give lots of room, and you would not need to modify the building. With no helper, you are wise to not go too long. If you are used to a TT, it may be harder for you to adjust to the way a FW backs up, since different than TT.
You did not mention what you have for a tow vehicle, but a bigger, longer TT may not work for you. That can also be an issue with a FW, as they require a heavier duty truck with a fair amount of payload.
Good for you, to continue camping, and taking a yearly trip on your own. I'm not sure I could do that by myself.
Jerry