Not answering your questions directly, but this is what I think.
1. Russia is ok with letting in supplies from the west. They've received assurances from the west that no heavy weaponry will be sent to Ukraine. Most of it seems to be coming in through civilian vehicles like 4x4s which is very inefficient. More than weapons and ammo, at this point they are bringing in food and supplies to keep 30 million people alive.
2. RuAF could absolutely smash Ukrainian ground units at this point. It would be a turkey shoot. They seem to be targeting the threats to them e.g. artillery positions which they are disabling slowly with UAV guided artillery of their own. Not as efficient as using drones but they seem to be lacking in that department.
3. As for why they aren't, probably because they don't want this to be a mass casualty war. Despite claims of tens of thousands of dead on both sides, casualty numbers are likely to be quite low for both sides. In the thousands rather than tens of thousands. Civilian deaths are also likely to be low. There will be exceptions - e.g. Mariupol where I think the deaths will exceed all previous ones combined.
The death blow to the Ukrainians are the PGM strikes which are focused on logistics hubs, railway depots, warehouses, depots, and any remaining anti air equipment. Once in a while they target a barracks or reddit battalion for propaganda value.
Countries normally rely on sea shipments for food and other essentials as it's the cheapest way. Transporting it by road in small vehicles is very expensive in costs of fuel, vehicles and drivers and is not sustainable in the long run.
Rather than getting stronger with time, the Ukrainian army is getting weaker. Rations, ammo will soon start to run low and morale will drop. Every tank, APC artillery unit they lose can't be replaced, and at some point, soldiers will have enough, ditch their uniforms and flee.
Time is on the side of Russians, assuming Putin manages the domestic situation. That is Putin's forte, there's no sign of any major civilian discontent at present. Protests have small and easily quashed, and seem to be the hippy anti-war type rather than regime change. It's also a geopolitical battle, which again is Putin's preferred battlefield and he's making Biden et al look divided and incompetent.
I don't think any Russian general will be happy right now as its not how Russians typically fight, but it's ultimately Putin's call.