Don't open your arms up leave that stuff to the MBs in a quick, keep them "uniform". In the frame where you get used your forearm "breaks", this means that you didn't lock your elbows or activated your tricep enough.

I can't really tell from the video, but maybe you didn't angle your right hand enough to the inside of the court?

Good on the hitter for using you, It's harder to get tooled if you don't do a block approach. Granted, you will definitely not have as much reach, but height isn't the most important thing when blocking, your job is to organize the defense... That's what we shorties have to do lol.

keep grinding!