Part 4 is a support that runs from a frame extension mounting bolt (with a spacer so the support clears the side of the frame extension) up to one of the mounting bolts for the steering box.
Not a very good photo, but you can see part of it in this shot
Part 5 looks to be the support that runs from the bottom edge of the dash back to the end of the pinch "bolt" for the uppermost column clamp. That's the "bolt" where the other end attaches to the brace between the dash & battery box (your part 11 I believe). Sorry, I don't have a photo of it.
Parts 7, 8 and 9 I don't believe are part of TR3A steering. (Looking at the TRF web site, I think they might be for TR250/TR6
https://trf.zeni.net/TR6-TR250GB/114.php?s_wt=1540&s_ht=963 ) On a TR3A, the only felt is the bushing at the uppermost end, and it is usually supplied in a trapezoid shape (ends cut at 60 degree angle) rather than rectangular.
The two rings in item 10 I believe would only be for an earlier TR3 with the solid column. They go inside, between the shaft and outer housing; but I'm fairly certain they were not used (and would serve no purpose) in the split column.
Part 1 might be one of the two support bushings, that go immediately above and below the "split". (The same bushing is used in the TR6 steering column.) Part 2 I don't recognize, though.