I think I have solved all of my triangle problems. Warning, I am definitely "twitching the veil" on this.
Firstly the pattern part, after mulling a while I had a brainwave! The problem is that playing fast off-beats is very hard, especially when mixed with on-beats. I considered slowing things down foor recording and then speeding them back up again. I was concerned that this makes the natural ring of the triangles shorter. I am recording the 5 triangles as a track each. What I actually did was rearrange the pattern so that the off-beats were all played on two of the 5 triangles, and those two only played off-beats. I worked out the pattern and played those as on-beats, and then shifted the recordings so that they were now on the off-beats. I consider this to be elegant cheatery.
The second bit was the cutting off of the delay, I decided to try a different approach which is "realer" than the original rather than elegant fakery. I again had the jangly bits, but stopped them dead by hand, waited and then had a single hit where I wanted the ringing bit to come back in. This had exactly the effect I was looking for with the planned editing, a tightening up and then a release.
Thirdly, the first section, the "free-for-all". I shortened it by introducing a clock winding at the beginning, which I wanted somewhere anyway. I was thinking of having it at the back end of the previous sub-section, but this way seemed to make more sense. This means the triangle free-for-all gets going slower. There is a little more structure for the free-for all but not a lot, that little bit shorter really helps. And I also used a technique called "when you think something might be boring, add something else to distract from it" - I added a nice backwards electric guitar chord, something I felt like I had wanted somewhere in this sub-section anyway.
The other thing I added was a wood-block being played, starting when the triangles pause after the jangling bit. Actually it's not a wood-block but I don't know what it's called. It's wooden, and shaped like a tube with a split up the side. It's ridges so you can get noises rubbing a sick up the outside, or it rings in a wooden way when you hit it. There are two of them on one stick, which hit alternately sound like "tick-tock" - which is why I wanted it. I'm sure I could have found a sample of the soound but I wasnted to record it, straight through proper live recorded instrument.
So the final (maybe) structure of the time sub-section goes like this:
Triangle at the start, clock winding. as the clock starts ticking there is a triangle free-for all. in the background a reverse guitar chord comes to it's climax, at which point a rythmic complex pattern is played on 5 triangles. After some repeats all triangles jangle and are held. The tick-tock starts, the triangles have a single hit and are left to ring. Drums come in with some fills, settling to a regualr pattern, behind which the guitar chords fade in. There is a drum fill, the tick-tock stops (not the real clock SFX) and then the guitar soloing starts, accompanied by guitar chords and bass drum only. Solos for over a minute, end of sub-section.