Regarding cost of a new phone, you may want to try something in the Samsung Galaxy line. I hear good things about them. Sort of like an S7 lite, I believe.
The whole Samsung phone line is Galaxy something or other. the S7 and S8 are, properly, Galaxy S7 and Galaxy S8.
I think you are probably referring to the Galaxy J line. The Galaxy S series is the Flagship Phone, and the Galaxy J series is their more mid priced line pitched to the low cost carriers.
FWIW, the Galaxy S9 drops next week so the GS8 is down to $600ish, and the GS7 is also dropping. My GS7 has been a great phone, although the last software update slowed it down dramatically. Battery life is starting to drop after 2 years, but I still get a full day of use, including streaming a couple hours of music and have 40% charge when I get home, so it's pretty good. I would recommend one as a solid smartphone choice.
I'm a huge fan of Samsung phones.
Due to size , build, battery requirements, and more phones being waterproof a user replaceable battery (at least replaceable without a soldering iron) is pretty much a thing of the past. There are some hanging on, but none of the really good phones have it. The form factor and builds are too small to do that and remain competitive.