Yeah, I'm a little more than proud of myself. Called Jones' Typewriter and talked to Charlie, who said my best bet was to bend the link bar so I could get enough leverage to hook both ends into their respective holes. Now I can use 3 and # again, which is great since I'm 300 something pages into the novel and kinda need that key.
But it came with a price...
The type bar no longer returns to its full rest position. Not sure what's interfering, but the "1/" key has the same issue (although the latter is frozen in place). I may have been too enthusiastic in my bending.
I also fixed the right margin stop!
See the two screws and the piece of metal marked "18"? That comes off, leaving the margin marker itself behind. Turns out you have quite a bit of room to maneuver the metal piece because the holes are bigger than necessary. So, all I did was loosen the screws and push the piece down until it was able to snag the margin stop without getting caught on the bell lever.
Once I figured out how the darn thing worked, the total time it took me was less than 15 minutes (it just took me three days to figure it out). I can see why so many people love the SG3. It's like the AK-47 of typewriters. So easy to take apart! I'd probably have never gotten this far with any other model.
There's still work to be done. I cleaned out the mice fur, but the inside is still a bit dirty. The spots on the outside did not respond to penetrating oil (maybe I used too little), and the "1/" key is frozen (not that I'll be using that much).
Other than that, this machine is ready to work! I'm anxiously awaiting my Olivetti 21 to come back from the shop. My Lettera 32 has been filling the gap in the meantime, but I've gotten accustomed to using bigger machines for my writing, so now I'll be switching to the SG3!
My SM3 turned out to have more problems than I thought, so it'll be going to Vern soon.
Power to the pen!