Yes, they will still support him. Republicans dying of COVID would still deny its existence on their deathbed, so you can be sure there is no consequence that is too far for them. Farmers bankrupted and people who lost jobs because of Trump's policies continue to support him. Inflation is bad when Democrats do it, but it is fine if Republicans do it, as with all things, because that is how their hierarchy works.

Their support is not the result of a rational calculation of self-interest, and never was. If it was, a base of rural and poor people would never be supporting a coastal city New York elite born with a silver spoon in his mouth as "one of them". But they do, because he is one of them in the way that matters to them. They are fighting for something larger than themselves, and are completely committed to a cultural war for social hierarchy.

> if gas prices and general inflation spike hard, as is nearly a given if Trump doesn't back out from the war?

As an aside, I don't think there is any backing out of this war. If somebody launched a missile at your country and killed hundreds of schoolgirls, and destroyed ships on diplomatic missions while leaving the survivors to drown, while also assassinating your country's leader (but not out of any intention of liberation), would you just let things go because they stopped bombing? Of course you wouldn't. Your country would continue to retaliate. And it is trivial to punish America. Even if America unilaterally decided to "declare peace" and withdraw from attacking Iran, Iran has every reason to continue locking down the gulf and making Americans pay the price. Unlike with tariffs, there is no backing down from these price increases even if Trump gets cold feet. But, even so, there is no reason to believe it will move the needle on his base. There is already talk of "short term pain for long term gain" among those who realise this.