Floating point should be no problem, unless there is some really crazy math. Even if you must use some crazy math, you can use Compilation that compiles your JS code to C and runs at C code speed.
Haven't used, but the DPS310 has an impressive promo video.
Or (I guess you already have a Puck, so suggesting another buy is not really nice) you could by a Ruuvitag that's pretty weather-proof. Altho' the onboard BME 280's datasheet says it's relative accuracy is +-0.12hPa, that's about 1 meter, that's not as good as you would want.
allObjects could be right, not sure how much error would be due to the silicone cover's resistance in such small pressure changes...