Karen,
I just finished downloading the owners manual for your machine from Singer. There is NOTHING complicated about threading it.
It's a standard thread pattern used by Singer for years with their machines. If you cannot get it threaded then there is something blocking the thread in the tensions, (lint, fuzz, oil, grease, dirt, ect) or you are doing it wrong.
In this case you don't even have to read, just look at the pictures. Perhaps a magnifying glass would help, as the original manuals are a bit small. I'd suggest going to the Singer site and downloading the large size .pdf for free so you can see the thread routing easier.
{
http://www.singerco.com/uploads/download/690_7110.pdf }
Not picking on you, just being honest.
As for the presser feet, the Singer snap on feet with the thin adapters wobble, nature of the design. I have several slant and low shank machines that use them and they just are not as solid as the all metal non snap on feet. If it doesn't cause trouble use 'em, if they do, replace them.
Joe