It's not clear that he really said it. And he might have already known that the universe wasn't infinite. As of now, we would say that the observable universe is about 93 billion light years in diameter and the unobservable universe might be anywhere from 250-1000 times that size. But we don't have any more accurate measurements to say beyond that. In theory it could be infinite beyond that as we don't know how big the universe became during cosmic inflation, some claim it could still be going on in some other part of the universe.
https://www.snopes.com/fact-check/einstein-universe-stupidity-infinite/
https://www.forbes.com/sites/starts...how-large-is-the-entire-unobservable-universe
So now you're getting into string theory?
https://en.wikipedia.org/wiki/String_theory
Well if you don't want to crazy with that 150kw generator, then a 9.5kw generator from Harbor Freight is about $2400 and if you could run it at max, they say a Model 3 is about .34kw per mile of range so if you fire up that generator, you'll get about 28 miles after an hour. It's dangerous to just be sitting broken down by the side of the road, lots of drunk drivers hit parked cars all the time. Probably better off to just tow it away to a safer location.