New to 3d printing and wondering if anyone knows how to fix this jam issue

[Ben Weimer]

So I am knew to 3d printing and I've had mine for about 2 weeks.
I have had a monoprice select mini but its been heavily modded by its past user unfortunately I am not sure what hot end he put on it (i'll attach a picture so if anyone knows).

So at first it worked fine after some bed leveling, but when I tried to do some longer prints it would consistently jam after about 30 minutes. After some research I decided that the issue was probably heat creep or a nozzle clog. So I decided to try doing some cold pulls to see if I could unclog the nozzle, and the filament refused to come out unless I heated it up to about 90-100C . And this is when I found my issue (or one of them idk). When the filament was pulled out it had a torn disc of filament right in the gab where the nozzle and heat brake meet. Since the nozzle and heat block were way to clogged with plastic to adjust I set about thoroughly cleaning out/off the entire hotend. After I cleaned off all the plastic and could remove and clean the heat brake and nozzle as well as getting all the plastic off the heat block I reassembled everything (while hot). and tightened it all down as much as I dare. Now while the leak between the heat brake and nozzle is significantly reduced it still mushrooms out a little bit between them. The filament between the nozzle and jam is also really marked up with little holes (that don't go all the way through).
I've tried tightening down the nozzle but I'm not sure how far to go with it.

I am also open to getting a whole new hotend if necessary just A. want to make sure that this one isn't going to work and B. get the right one.
if you need anymore pictures of anything let me know.
The first picture is what the filament looks like when I try doing a cold pull. The second is my hotend.

Any help comments or questions would be greatly appreciated,
thank you.