I started similar to you, except that after I built my MAME, I got into vids and collected those for a while before moving to pins. I will warn that wiring a MAME is electronically not similar at all to a PIN. A MAME is typically going to be simple wiring using your typical PC, cheap crimp quick disconnects and store bought cables. Soldering and PCBs are a whole new ball game. (Not saying you don't know what your doing, just making sure you are going in with your eyes open)

As for the specific game. LW3 is already typically an inexpensive game, and with all the problems this one seems to have, that price seems a little high. I am not sure where you are located, but I paid $700 for mine, and it had no major issues, and I am located in what is considered one of the more expensive pin markets.

Yup, could be a larger board issue. Which can get complicated and costly.

By the way, the DMD, looks like it is outgassing. Which means it is not something that can be fixed. You would either leave it as is and just play it like that, or you would need to buy a new DMD.

I didn't even notice that until you said something, and now it is staring me in the face. Yea, that definitely is not a good sign.