I used to run the 1700 sets around the tree with just a circle of 072 track. No straights so the train could fly.
They are neat.
For the sliding track, consider Johnson's Rubber Roadbed. It's like the American Flyer roadbed, but made for O gauge track. I just checked downstairs, I have lots of extra O straight, but no extra 031 curve. It's adds weight and friction to the track so it doesn't slide around as much. For the track coming apart, pinch the rails together with dikes.
Here's Johnson's roadbed on some track:
Here's a sequence showing how to crimp the rail with a diagonal cutter to make the track stay together - my crimp is exaggerated so it shows up in the photo. You only need to slightly deform the tubular area of the rail.
Depending on the age of your track and how much use it's seen, you might not have to do all the rails on each section.
When I was buying the Johnson's roadbed on ebay I was trying to get it for under $3 a section postpaid. Ebay seems to be down right now - maybe all those T-day shoppers! - just search for the phrase -- Johnsons roadbed lot --
Maybe I'll set the tree up this year.