1. If you cannot complete the repluse move, you cannot start it. You don't get to do the recoil bit of it then stop. If repulse is your only option, then you have to stand still. Some troops have the option to repulse or recoil, in which case they could chose to recoil instead.
On reflection, I think this is the opposite of what the rules say. They say:
"The repulsed element first recoils.
If certain condtions are met, it then moves back until it is its tactical move distance from the enemy"
The only conditional bit is the part after the initial recoil. The implication is that if you can't fully repulse then you stop after the recoil bit.
2. Hmm - tricky. I would say that it should end up its DGo move back, in the GGo. That is the principle that is applied to normal moves. The Commentary ruling seems a little bizarre, but there might be a reason for it, so I would rule in line with the Commentary, but I will have a look at the Commentary ruling to see if there is a reason for it.
Having thought about this some more, I think the best way to handle it would be to say you move back the minimum of:
The distance you would go if you made a full tactical move back from the enemy;
The distance at which you can just reach the enemy if you make a tactical move towards them.
You stop after the recoil if:
You pushed friends back while recoiling;
You can't complete the move back without contacting the listed items;
You are already beyond a tactical move from enemy (could happen if repulsing from long range shooting).
In that case the result is the one you describe, i.e. the commentary section on stopping short of terrain would apply (An element that would reach DGo or RGo from GGo with its GGo move will only move its DGo or RGo
move distance (as appropriate) although this may cause it to end its move some distance from the area
feature.)
This would be a change from what the commentary currently says on "repulse", but I think it would still be consistent with the rules and cover most, if not all, repulse questions and make the commentary self-consistent.
IMO repulse is more complicated than it needs to be because of the exact wording used and the strange way that the movement system works when you reach terrain. The equivalent rule in FOG amounts to "Move back as far as possible as long as you can still contact the enemy". They do not impose a requirement to go back a full move, and you can stop short of a full move if obstructed.