Despite having a high position and high competence, Georgi Zhukov survived Stalinism.

Mostly, but he had a few close calls! I'm a bit busy to answer all of your questions, but I've written on some of them before.

Especially for the last one, while I think that the dichotomy you use is a bit ill-suited to discussion of the Soviet political landscape in which he existed, the picture which we see painted is not of a man who wanted the top job for himself, but was committed to upholding a system in which he certainly seemed to have an honest faith in. If anything, the way in which he went about this evidences something of a naivete and a certain level of blindness to the threat that others would nevertheless take him to represent. This older answer of mine goes into more detail on this and I expect would be of interest for you here.

As for your first question, that is a bit more complicated and I wish I had something direct to toss over your way, but this at least I think is highly relevant as it speaks to his rise in rank and engagement with the worst of the Stalinist system during the purges. His clear benefiting from the culling of the Red Army ranks in later years was a clear source of embarrassment for him and something he did his utmost to downplay, but at the time at least, he at the least wasn't so morally troubled as to refuse benefit of it.

Pivoting more personal, this answer regarding the allegations of religious belief might also be of interest, as it is actually a somewhat fraught topic given the way by which we come to the descriptions. I'd also add briefly of course that on the personal level, he was a philandering bastard, with a number of affairs through the years, and children by three different women, all while married to the first.

Hope that offers some insight!