1. That physics professor (Cambridge) was wrong on some things. I do wish I had $10 for each time people have told me I should read his book because it would explain to me why what I (and others) was trying to achieve in renewables (or BEVs for that matter) was doomed to fail. Unfortunately his work has been quoted many times by the anti-renewables people as a good reason why the world should stay on dino-juice. He is dead now so he cannot write an apologia.
I believe it was David MacKay who died a few years back. I thought he made some good points, and he wasn't anti-renewables. In fact he professed to be very pro-renewables. I don't have time to rewatch the talk now, but if I remember right his point was that all renewable energy sources were fairly low KWH/m^2 of ground compared to other sources.
It's quite possible he was wrong, but a deconstruction of his case is probably the subject of another thread.
2. Simply getting the ships safely into port and the troops etc offloaded would take one day. Getting them onto trains in the correct order would take another day. Then go look at a map of the Russian rail network, look up the capacity of the rail switching yards, look up the average speed of a Russian goods train, look up the headway between trains on Russian networks, look up the availability of railway wagons in Russia, think for a moment about the likely rail network congestion as you work your way anti-clockwise from Crimea around to (approx) the Belarus border .... and accept that it would take about a week to do properly (minimum !). There is a reason they say that WW1 started because of railway timetables, and they are not wrong. If you go back to my post #549 on this thread you will find a note I wrote here commenting that the Russians were going to experience difficulties with lateral troop movements (such as this suggestion of yours).
Unlike WW I flying troops to a new location and have them take over some other units vehicles is also an option. Though, again, it's possible they have not been transferred.
3. Yes, some marines units will likely be in the North since the beginning, but not a full-on redeployment.
4. I note the fact of what is happening, as far as I can observe them. I deliberately do not suggest (much) as to how the Russians might improve things (except for surrender / run away / make amends). If you look around the OsInt networks you will see similar caution and restraint.
Whatever happens the Battle for Kyiv is going to be brutal. Flattening a city and then rolling in works when the defenders have been demoralized by the bombardment. The Ukrainians so far seem to be reacting like the British did during the Blitz and the Germans did during Allied bombing of their cities.
The Russians have an advantage in vehicles and artillery, but both of those are muted when the troops enter the city. And the Russians probably don't have a numerical advantage in troops going in. In an urban fight vehicles are often more of a disadvantage than an advantage. Armored vehicles are stand off weapons, when the enemy gets close bad things often happen to the vehicle. And calling in artillery strikes when your own infantry are engaged with the intended target is usually risky. Considering how much trouble the Russians have had with communication and coordination, I doubt they can call in artillery strikes with the efficiency and accuracy NATO can do.
Dumb artillery rockets are not precision weapons.
Kyiv might end up looking like Stalingrad for a while. Maybe the Russians solved their supply problems when nobody was looking and their forces are adequately supplied? That is possible.
But force numbers don't lie. The Russians brought around 200,000 troops to this war, which is 80% of the entire standing Russian army combat force. They have reserves they can activate, but that's going to take time to gather them, arm them and send them to the front. I have not heard any stories coming out of Russia that there are any significant call up of reserves. Leakers have said that Putin doesn't want to call up the reserves in case the public starts to get wind of how bad this war is going.
The Ukrainians have 300,000 regular troops active now with foreign troops coming in. The foreign brigades may not be sent directly into combat, but may be held in rear areas allowing more Ukrainians directly into the fight. The Ukrainians also have thousands of organized militia armed and ready as well as many unorganized militia who are civilians who were given an AK-47 and some molotov cocktails. The civilians are the least reliable troops, but there are a lot of them and they are very angry. They will do some damage.
The Ukrainians also have excellent intelligence on what the Russians are doing. They have a hotline people can call with information on Russian troop movements. This may have contributed to the Ukrainians hitting some of the Russian supply convoys. The Ukrainians are also listening to most of the Russian comm chatter because the Russian encrypted system failed. That is also contributing to Ukrainian intelligence about Russian troop movements and plans.
Except for the Russians nuking Ukraine until it glows there is no scenario where a smaller force with generally poorer morale is going to beat a larger force defending their homes with good morale.
The Russians did not bring enough infantry to hold Ukraine. Their only hope was Ukraine was going to roll over and give up. That didn't happen.
It looks like the Russians are going to get a lot of people killed (on both sides) trying to take Kyiv. The next few weeks are going to be very messy in Kyiv. As long as the Ukrainian morale doesn't break, the Russians are almost certainly doomed. When the defenders are in the mood of the Ukrainians now, they don't break.