I play on 1600 x 900, and I can't exactly reach sub 20 (Easy), I'm not sure if it is myself, and practice or if it is the resolution. Is everyone playing on the highest resolution? Or am I just crazy?

Nah watching your submitted run, the main problem is you're not using the fastest strat. Also, boomerang is good because it comes back, if you throw it at a blue balloon it will come back to pop the red balloon, you don't need to throw again. This combined with lining up balloons correctly makes using boomerang initially good.

ok then, thanks.