Be carefull who you listen to when you ask for feedback from others. However good intentioned some may be, they think they know, but they do not know.
here are a few things a noticed from your video. (you didn't even have to pay to go to umpire school for this advice.
---Before you walk in behind your catcher, put your mask on. It should be on and ready to go before you even start to walk behind him. Then all you have to do is get in slot and wait.
-----Timing is quick at times. proper use of eyes will take care of that. See the pitch all the way to the mitt. Do not be in a hurry.
-----hold indicator in hand with pointer and thumb, not with pinky and thumb.
-----put arms up at same time, and signal with fingers at same time when giving the count. 1 ball 1 strike.
-----regular strike mechanic is too high. keep it down just below shoulder if you are going out to the side like that. still be visible with it , just will look much better.
----you look good in your uniform. nice and clean and well fitting.