Have you considered bone conducting headphones? Since they don't actually cover your ears you stay cool, and if you want to block out outside noise they come with ear plugs. I wear mine constantly.
Shokz OpenMove headphones are around $80 https://amzn.to/3LgYCq8
Resolume comes with Alley, a free (as in beer) converter that will convert to DXV3 format, but it only supports input formats that Resolume does. If you install the HAP codec on the computer you get a FOSS codec that works great and is supported by FFMPEG. Works great in Resolume.
Have you looked at the Morserino-32? It does all of the things in your main list at least, as well as quite a bit more.
Another option would be the (tr)uSDX which is a 5 watt transceiver. Has all of the settings you are looking for, and can be set to practice mode without transmitting. Even has a CW decoder built in. This is what I personally am using to practice.
Hope this helps 73 de N5DEW