Part of your problem may be the plywood replacing the broken board in between the bench seats. Is it the right thickness, or does it create an indentation because it doesn't meet the top of the built in benches? If not the right thickness, you could build it up with a second board, glued on top, of the right thickness and improve your sleep.
You may definitely benefit from replacing the cushions with a mattress, especially since you "full time." You might consider a really good quality twin, and use the leftover space on the bench top for drawer units or a "night stand." One of my friends did this, and loves the extra space. Her Casita
, with a twin instead of the full, feels like a veritable dance hall with the extra floor space! Again, even more important since you full-time.
Even a great quality twin is not too heavy to lift up for bench storage access.