Before I address the specific situations, let me throw out some general thoughts about the cards in
VB. A YC in a
VB match is nothing more than a formal means of communication to say: "That's enough and this is your warning." There is no penalty associated with a single YC. My thought process is if you are questioning whether or not you should have issued a YC, then you probably should have. Unlike baseball/softball, where your formal options are limited to restriction to bench/ejection, the YC in
VB can get your warning message across and also indicate that you are serious about the behavior stopping.
For your specific situations:
Coach and several players jumping off the bench screaming about a judgement call - Issue the YC immediately after the rally is concluded. Issue the card to the head coach as they are responsible for bench conduct. Mentioning it between games might have done more harm than good as it was you bringing the situation back up when the coach may have forgotten about it and moved on. Since you don't know specifically what was said between the two coaches at the start of the next game, you really don't have any reason to issue a card at that point.
Next match starts, the warnings sequence starts over as well. You can't carry things from the last match forward. I know this is easier said than done, but it has to be that way. From your description of the situation, I think a verbal warning is adequate. However, I would have directed the warning to the 7th grade coach as she is now the head coach for this match and responsible for bench conduct.
As for the derogatory ace cheer, a verbal warning to the team captain was probably in order, depending on how derogatory the cheer was. Just let the captain know that if you hear that cheer again, cards will be issued. If you feel that a card is warranted, issue it to either the coach or the captain as they are the leaders of the team.
As you gain more experience in
VB, you will get feel for when a verbal warning or a card is necessary. You are thinking about it now and learning as you go.
My experience has been that middle school is the hardest level to officiate as far as dealing with coaches because some of the coaches use the role models they see on TV in college and professional sports as their baseline. However, working at that level will provide several different experiences and learning opportunities. Just keep at it!