The max limit is for the entire route.
At trainsim forum, in the "Merging Routes Tutorial", ATSF explain why the limit is 65535 for dynamic tracks (24/09/2012).

I take a look to your route. Your local TSecction.dat have 25872 tracksections n° 40002 to 65870, I think that you have reached the max limit of DT. If I delete this file, I can put a DT without crash. Sorry but rework your route with less DT.

I send you 2 requests, the first have a blank message.
What is your version of TSRE, mine is v07.007

Like eolesen write, use the "Tools -> Errors & Messages" feature. In the video, the junction node 259 is not linked to a track section, TSRE report an error. Correct all errors before more investigations. Try to put a DT anywhere on the tile, hit Z key and see what'happen. If TSRE cras...

I agree with Garry. After try to put the DT from the other side (tracknode 112) with a negative value for the angle, 2nd straight section became 1st (MSTS heritage).

You have a strange yellow line with no trackshape which terminate in the upper center of the second screen. Try to remove her. - remove from TDB the adjacent(s) trackpiece(s) (Z key) - put a trackpiece at the end of the yellow line - use the HACKS fonction (sometimes click many times) - after the ye...

Good idéa, the same thing for the radius, standart spacing between 2 tracks is 4,985m.