Ukraine is a big country compared to other European countries and is hard to occupy due to its size and the fighting spirit of its people. If there were no more soldiers, how can the Ukraine be fighting battles on many different fronts?
Ukraine has inflicted so many casualties on Russia that Putin is looking as far as North Korea for help. Putin will know that to continue this war will eventually deplete his military so much that there would be little chance of any military success against the rest of Europe, via conventional means.
Trump actually was the first POTUS to allow Javelin missiles to go to UA in 2018, after Obama (and Biden) did not. He gave NATO warnings about budget shortfalls about the same time - he has been consistent with this complaint - I do not think he would abandon NATO.