You're smart to be cautious about spray foam. I used it myself, but the trick is to choose low-expansion foam specifically made for windows and doors....

Draft snakes are decent, but honestly, I've found they're pretty limited if your window gaps are bigger or uneven. I tried one last winter—similar DIY...

That's exactly what happened to me last summer. The foam tape I used basically disintegrated after just one season in direct sunlight. Silicone strips...