You can't glue in the back unless the side grain is running vertical. But I wouldn't do it anyway, as if a repair inside the carcase is ever necessary you can't remove it. I think screws are better, but nails can be used, too.
If a jointer is in the budget, a 6" used one will be better than nothing, and are pretty cheap.
Personally I would address the glue joint with a #7 jointer plane. If you think this is a possibility for you, check around for a used Stanley, maybe a rough one that needs refurbishing. I will warn you in advance to be very careful, as these long planes can be warped DAMHIKT.
OTOH, if you're really serious about it, I believe a WoodRiver #7 will run you about $350.
Regardless, if you plan on jointing lumber without a power or hand plane, there ways to do it with a router.