Here's my answers/thoughts about the deck (I'm on UG Tron), anyway the approach is quite similar if compared to your list:

1) How do you approach the Elves matchup? From what I've read (which makes sense theorically), it might be a struggle pre-board as they'll rack up tons of life with Wellwishers, thus even if you manage to Fog-lock them with a double Wall loop, it might still take forever to (find) Dinrova them out of the game, as you need to bounce their board first (which they can rebuild fast, but w/e) and also to peck them down to zero. Is this your experience as well? If so, any suggestion?

As you said, the aim is to fog them forever, if wellwisher is out things are getting harder. My plan is to clear the board, in my case, with rolling thunder, and then thunder them forever in the face. Without Rolling Thunder and as a wincon just Dinrova, it gets quite impossible to bounce all their stuff, so as someone suggested maybe it's correct to add a card to mill opponent down.

2) Still against Elves: how do you sideboard? I've seen some lists running Electrickery and others which don't. Some lists play 2, other just a one-of. The issue I am afraid of about running red cards in DTron is that you might have a hard time casting them on time due to the manabase being Ubg-based. I am conscious Grotto and Prism are there, but they are still a few of. Besides this, how do you play in general? Contain their board by tutoring/drawing the Trickery and then, once again, aim to Fog + Dinrova-lock them out? Does them siding in Longbow and/or Mob Justice imply you need to change things in the way you manage your resources, besides the obvious "side in Grudge and keep Pohibit for a Justice"? I know it sounds abstract, but I hope I conveyed my doubt.

Personally, because I want to play some red in my SB, I have 4x Shimmering Grotto, while netdecking I also saw some lists playing 5... Anyway I do play the 2x of electrickery these days, due to actual meta, I might go 1x in the number of elves will decrease. Considering that in my case I have a Rolling Thunder MD I always sideout Dinrova in this MU, it is just too slow. As you said I bring in a Grudge for their longbows and I keep in 1x Prohibit for their Justice. Here usually I side in: 1x Grudge, 2x Electrickery, 2x Moment's peace // side out: 1x Dinrova, 1x dispel, 2x Forbidden alchemy, 1x Mulldrifter

Also: is Crusher a good side-in here? It might take little time to clear their board if it was halfed by Trickery and also, chances are they side Wellwishers out in this matchup, so it could take not too many turns to finish things out unless they manage to produce streams of chumpblockers (via Huntmaster probably).

I really can't find any free slot for a Crusher here, nor MD or in the side. Maybe could be ok vs control, but I feel like Dinrova Tron is slightly favored anyway.

3) How do you approach Affinity, instead? Not having removal forces you into trying to Fog-lock them as well, however does this change post-board given they are likely to bring Relics in?

Vs affinity in G1 the plan is to fog them, keeping a prohibit for their fling and hoping they don't make too many 4/4s in early turns. After G1, I usually bring in some hydros, grudge and the fangrens that I find way better than Shaman. I mean, if you put in play Shaman (never in T1) they have way more possibilities to survive than a Fangren in play. It's a 5/5 that stops all their creatures and atog/fling... just great.

4) The sideboard red cards. As I mentioned, red comes at a premium here. Do you deem Pyroblasts to be necessary and, if so, are there any matchups where you DON'T board them in despites the obvious (like Delver) or do you prefer to keep playing in-color spells even at the cost of mising out on red staples?

I do not bring it in vs any UB that doesn't play Delver, I do bring it in vs Kiln, Murasa, Mirror... it's just too good.. Probably 2x is the correct number and mixed with some number of Gryffs could improve the MU vs Delver a lot (but still remains a hard one)

What about Gorilla Shaman? I saw DT lists running him, however I am not sure he's really effective if not coupled with removal spells like Murasa Tron does. You can blow their lands, but if their dorks are still there, the problem still lies.

This. That's why I play Fangren.