I wrote a long reply but lost it just before posting!! Anyway here is, he short version.
Did you ask H about the poem, what it meant to him or why he shared it with you? Maybe you should. You may not get any clarity. Probably won't.
Here is my reading of the situation. H deep down wants to reconnect with you. He may not know that and definetly doesn't know how to go about that. Maybe he doesn't believe he can reconnect with you. The problem is that half hearted sporadic gestes like this can never achieve that. He us setting himself up to fail and hence prove himself right.
I imagine it took him some effort and time to send that to yo. He probably hymed and hawed for a long time. Then he sends it and you ignore it for a full week. OK I know you didn't but to him he probably thinks that you did. He would have liked an immediate response and as time passed it probably bugged him, adding to your recent interactions.
I am nit saying to fall over backwards nor to make a big deal of this but IMO it is another but bigger attempt to let you know he would like to connect. 8 will admit I am reading a lot into it. But there has been a patternand he has reached out before.
Neither of you are in a place where reconnection is possible at the moment. Even so if you see and react well to all attempts to reach out to you, you could help drastically improve interactions.
I say this just to try look at things from another perspective and I admit it could just be some meaningless act of a madman.
I think you did well in your other interactions and you were right to call him on his behaviour using son. He may not like you having done so but his esteem of you will have increased despite his reaction.
What can you do to stop his music choice affecting you so much?
And yes that was the short version!!
R 25 years M 14 years S11 & S13 Working on it alone since Oct 2014 M in trouble a lot earlier (~2 years) Feb 2016. 1st R chat in a yr. Next R chat Aug'17 Still together