He may not support war but that doesn't mean there won't be one. If China attacks Taiwan, or if North Korea attack the South there will be a war in which the US will take part, despite of whoever they choose to be the president. There will also be a war if Russia uses nukes or of Russia attacks a NATO country...
IMO Biden has no chance for reelection. He's too old and is proving to be weak. A weak president makes the country look weak.
Theses two scenarios (Taiwan and Korea) are not 100% guaranteed. If China invades Taiwan, then we can expect a retaliation from the Americans. But I am not sure whether the US will declare full fledged war against China or not. Same with the case of Korea. The US in all probability will send military and financial aid, similar to the way they are doing in Ukraine. Any direct conflict with China or DPRK will result in hundreds of thousands of American casualties, and at this point the US can't afford that that many casualties.
Now coming to Biden, I would say that his chances look much brighter now. GOP is in shambles. The situation is similar to what we had with Dems, after the 2016 primaries. Back then, Sanders supporters stayed at home, resulting in Trump winning the elections. This time, it is going to be the opposite. Irrespective of who wins the primaries (Trump or DeSantis), the losing candidate will refuse to support the nominee, and this will result in Biden winning the 2024 POTUS elections.