The general consensus from alot of the 'geopolitical experts and commentators' I've been watching and listening to over recent weeks is that alot of fluff and bluster from Putin...in all liklihood. We need to call his bluff. His plan is not to stop at Ukraine and he needs 100% of Ukraine so any negotiation made to call a halt to fighting now by ceding a chunk of Ukraine to him will be nothing but delaying tactics to give him some breathing space to regroup, re-arm before coming back for the rest...just as he did when we effectively ceded Crimea ignoring lessons of the past that giving into these people is not effective. And he wont stop at Ukraine...he has his eyes firmly set on all the ex-soviet nations, including Poland, so he needs to be stopped. And no point in short term-ism of dealing with Putin...he has a long list of other despots waiting in the wings with the same objectives. This is about reclaiming the physical land boarders and barriers around Russia to protect their boarders from a ground invasion. Russia has no physical features like mountain ranges so its thousands of miles long boarder is all penetrable and impossible to defend. He needs a ring of physical geographical and geological features to protect his boarders and for that he needs all the ex-soviet nations - yes its old school soviet era land invasion thinking, but that is their thinking and another indicator as to how stuck in the past they are - dangerously so. So we need to call his bluff or we are looking at the next few decades of constant conflict in that region that will keep racking up the body count and drawing more and more upon our resources. Having said that he is racking up some body count too and even Putin doesn't have an unlimited supply of bodies to keep throwing at the issue. He's already increased the drafting age and pulled in the North Koreans for some canon fodder.
In any case the capability of the Russian army and military has been massively over estimated constantly and at every test it's been proven to be not very good to put it mildly - in fact pretty embarrassing for the Russians. If it wasn't for sheer weight of number of bodies Putin has to throw at the war with a strategy of long drawn out war of attrition it would have been over months ago. So there is no reason to assume his nuclear arsenal is anywhere near 100% operational and at a state of readiness. Of course it only takes one warhead to get through, but any move to use Nukes by Russia will be a huge mistake and Putin knows it so he's not quite as trigger happy as everyone is fearing...that is what he's banking on...though I don't doubt he's capable of giving the order.
The level of corruption at every level of the Russian government is such that pretty much 100% of the military budget has been embezzled by those in charge to fund their lavish lifestyles, yachts in Monaco, Properties in London and all over the world etc. and there has been zero budget available for investment in military equipment both in terms of maintenance of existing equipment, training and ongoing development and improvement of kit since the downfall of the USSR. So its not unreasonable to assume that this has happened with their nuclear arsenal too and the chances are his nukes are just as dilapidated as the rest of his military hardware. And we have seen with the recent Royal Navy failed Trident test that these missile systems are very complicated and very maintenance hungry and part of the reason we maintain such a large arsenal with huge levels of apparent overkill is to account for a certain proportion of the missiles failing when fired. If we have, say a 30% failure rate of our missiles, then Russias is more likely to be 80%+. It is thought that the failure rate of his conventional cruise missiles fired in the war so far is upto about 80%...pretty terrible really.
Anyway the threat of WW3 will not come from Russia..it's China. China is watching with interest as it plans its invasion of Taiwan. So if the western alliances put up a strong coherent response to Russia then it makes the Taiwan invasion less likely and push their invasion ambitions out. If we appear weak and fragmented then that might just embolden the Chinese to move quicker.
We can see the current 'axis of evil' between Russia, Iran and its proxies, and China, and I guess North Korea too to a lesser extent. It is no coincidence that we have Russia and Hamas all kicking off at the same time...all these events are linked and driven by one strategy.