What worked for me was playing in the tub, then laying on your side, relax your muscles, breathe slowly and take it a little at a time. However, I did a dildo instead of a butt plug, that was easier with the lube.
I can relate to the lazy sex partner, I have one myself. I found that masterbation aids in the satisfaction aspect of things. Keep your clothes on, he can’t force you to keep them on. Tell him “you want my pussy, you have to learn how to wet!” I can’t help you on the one sexual partner side, umm I need different opinions.