If there is anything I have become convinced of over the past two years it's that there is no way an invasion of the Baltics would lead to a nuclear exchange.
NATO would have to send in conventional troops (or perhaps the alliance won't even exist any more in the way it does now by that point).
Trump seems serious about pulling out of NATO, which would reduce the nuclear deterrent to just the UK and France in a European context.
Your own reasoning does not make sense, on the one hand Russia is a war economy with production capabilities that the West cannot match, on the other hand they would have no interest in taking over countries that would pose far less of a challenge logistically and in terms of manpower and equipment than Ukraine did and does.