ESB has mono and production documents indicate one done for ROTJ-additionally Raiders had a mono.
It is correct that the 70 and 35 Dolby tracks are likely very much the same but until we get actual concrete evidence it’s impossible to say. The baby booms were filtering out the low end as opposed to an actual dedicated LFE channel. I will suggest that there are likely a few differences in range etc since the 35 was intended for optical and the 70 had mag tracks.
The definitive collection 93 mix was reputed to be derived from the 70mm mix before those changes were made and is what HairyHen has been working with.
There is an in theater recording of the 70mm audio. It shows none of the additions that were made to the 93 mix and appears to be identical to the 77 stereo matrix mix. For the 84 mix, only the one line of C-3PO’s was added. For the 93 mix, virtually all the effects found in the mono mix that were not in the 77 stereo mix were added - though no lines of dialog were changed.
Also, the mono versions of Empire and Jedi were likely downmixes of the stereo tracks (possibly the L, R, & C channels or the full matrixed stereo). By 1980 there wasn’t much point to having a special mono mix for the theatrical prints. 16 mm would be a different case, but one where a downmix of the stereo would be the simplest way to achieve. There is a lot of evidence of a separate mono mix for ANH, but I have never seen any for TESB or ROTJ. There is another mix for TESB. The 70mm seems to have been missing some music and effects toward the end and appears to have been missing some of the composited effects. Again, there is an in theater audio recording so we have some idea how it is different, though I don’t know of any quality archive of it.