OP, I'm not really going to comment on how you acquired your setup, I believe you.
I will say that a) no, don't vape that thing at 157 watts, just because it goes up that high. You may stress your batteries and also burn out your new equipment quickly.
Also, if I found *any* vape, I'd recommend (since you can't find the owner) cleaning it thoroughly and REPLACING the batteries, you don't know how old they are, you don't know how the drug dealer treated them (and the mod) etc. I would buy new batteries and proceed with caution. I'd also suggest as others have said, not going over 120 watts in that setup (which to me would be pushing it but I vape at low wattages.
As far as a new coil, I don't see that you need one. You don't need to get up to higher wattages, you need to run wattages that are comfortable/safe for your mod and your build is plenty low already.
Also, good luck moving forward (and hopefully the mod).
Anna