Sorry it took so long to get here!
I don’t have too much to add from what the others have said already - use the double jump more - if im jumping as cal im dbl jumping.
i dont go for buildables much as him, too weak and theres better things i could usually be doing, but if you ARE attacking buildables, don’t. stop. moving. you could easy let the other team gank/ body block, etc. you.
i also dont waste skills on buildables, especially the thumper.
and since you said you were having trouble landing the flashbang: pull a benny with explosives- jump and aim at the enemies’ feet. you’ll still get the blind and bleed damage plus the aoe damage, even if you miss the direct shot- far better that aiming eye to eye on an even plane and missing, allowing your shot to miss altogether.
I have more tips, but they arent directly related to cal, and i didnt have time to finish the video, sorry!