If Ukraine can reach the Sea Of Azov coast, then they can likely also drop the Kerch strait bridge completely (as it is likely within HIMARS range then), then Ukraine will also be in range of the Sevastpol port. That would make Sevastpol harbour untenable for Russian vessels, and all the Crimean airfields untenable for Russian aircraft. And the Crimea water supply in Ukraine control. In that situation I cannot see how Russia can supply Crimea in any way. A real concern has to be Russia using the six reactors of the ZNPP nuclear power station as a hostage if such a situation begins to develop.
The world reaction to Russia causing a radiation leak at ZNPP would probably be close to as bad as if they used a tactical nuclear weapon. China might cut them off at that point. But if they're desperate, who knows what they'll do.
Putin has put himself and Russia in a Kobiashi Maru scenario. There is no reasonable scenario where Russia can win this war. Their only hope would be for the west to give up supplying Ukraine and even if they did that it would likely just devolve into a long standing stalemate at this point. Russia doesn't have the equipment, troop quality, or supplies to mount a real offensive at this point. They are trying to conduct an offensive, but it's so weak it's not obvious they are on the offensive.
With time Russia can improve the output of it's ammunition and small arms, but they aren't going to be able to build enough vehicles to replace all those lost at anything approaching the same quality as the original equipment. They probably can't produce enough vehicles to keep up with combat losses and build up forces too.
Their troop quality has an even worse chance of improving. They can create masses of untrained, unmotivated people who can be prodded into suicide charges, but they don't have an NCO corp and they have lost a lot of officers. They also got most of their trainers killed in Ukraine. So they no longer have the ability to train an army. That's going to take a decade or more of peacetime to rebuild, if ever.
Russia can't win. They can hold on and try to hope for a miracle, but once Ukraine has the ability to go on the offensive again, their window for miracles goes from small to infinitesimal.
Russia is going to hit a manpower problem eventually. In WW II the USSR could afford to throw away lives. The Soviet Union had a population 20 million larger than the United States. Now the US is more than 2X the size of Russia. In 1939 the USSR had 169 million people and the US 148 million. The demographics of the USSR then had a big cadre of draft age men. They now have a smaller population with a small cadre of draft age men. Russia today has about 10 million men between 18 and 32, they have well over 15 million women and about 10 million men over 60. They do have a decent cadre of men 32-55, but those people are more likely to be the experienced workers they need to keep the economy going.
The more working age men they draft, the fewer people they have for other things like building weapons and just keeping the economy going. The older the people they draft the more they are going to have to deal with health problems that will make their forces less capable. In the west we are used to people well into their 50s or 60s being healthy and active, but that's an anomaly of human history. We have the benefits of public health education programs, a high quality diet available, and vices like smoking and drinking are on the decline.
Russia doesn't have any of that. The upper middle class often live a western lifestyle, but they are a minority, and a lot of them left the country. Most Russian men are in pretty bad shape by the time they reach 50 and are in clear health decline by 40. The life expectancy for Russian men is among the lowest in the world.
For the first time in Russian history Russia doesn't have virtually unlimited pool of young men they can throw into a meat grinder, but the leadership in Moscow hasn't figured that out yet.
Unless something changes in the Russian leadership team I fear that there will be an awful lot of fighting still to come, and some even worse situations than we have seen thus far.
Unfortunately I think you're right. Russia can still cause a lot of pain and suffering for Ukraine as their army fails.