That is all good advice. Another thing to check is if the thread is going through the thread guide just above the needle on the needle bar. If the thread is not going through that guide it can cause skipped stitches.
The needle size and the hole in the presser foot is probably not the problem on an industrial machine using at least size 69 thread.
Your machine is probably not a 1426, that's a long arm double needle machine. It's probably a 145 or 1245, those are all very common single needle machines.
No one lives forever, the trick is creating something that will.