You should be able to use a single XMR instance to service multiple CMS instances and their players. The v3 XMR version will work with v4.
I’m not sure why your screenshots aren’t returning - you’d first need to be sure that your v4 connected players are receiving XMR heartbeats correctly.
Date formatting for Mastodon was fixed in 4.0.5, and I can also confirm its working in 4.0.6 which we released yesterday.