There is no chance of the war spreading beyond Ukraine with NATO on full alert daggers drawn, Russia is not stupid
Putin is in a tight spot, he expected a show of force followed by a quick surrender, it hasnt worked out like that, serious resistance by Ukraine and weather turning warm making it difficult to move heavy equipment changes the whole picture.
He probably has enough to take Kiev by force if he wants to but what happens then?, occupying Ukraine, no, he has not got the manpower.
With Ukraine mobilizing the whole country and NATO arming them, eventually Russia is going to have to back down, Putin may get deposed, he’s not omnipotent, he needs supporters and they must be getting increasingly nervous.