Now I'm not a lawyer, but OwnIt is and she will probably agree with my opinion that less is probably more in any sort of communication.
I listened to a podcast a while ago that said that when in front of a court (where I know you aren't now) to first think about if the question asked can be answered with a simple yes or no and to not volunteer extra information. The example was if asked "do you know what time it is", the answer could be either yes or no depending on if you see a clock Opening your mouth to volunteer more information can first off annoy the judge and secondly will provide ammunition for the other side.
If you feel that a response is required, which you'll want to think hard on that, a simple "I acknowledge receipt of your email dated xxyy" while cold and perhaps confrontational does let him know that you got it and have read it. You could also add "will review with my advisors".
Another piece of advice that I got here I think was to first imagine that any communication you make, especially written could be brought before a judge as evidence.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells