Here’s a thread that discusses the distance issue (spoiler: its been raised now and then but no-one has definitive answer I’m afraid).
Difficulty overtaking could be Sticky Draft (a more talked about subject around here that doesnt go away) or you need to get those legs working a bit harder 
I purposely sit at the front of any group as I find it easier to stay in the front than stay in the middle. Having said that, all events will now use a new Pack Dynamic setting so that may help out - here’s the snip from the release notes for yesterdays update if you havent seen it already:
Pack Dynamics
- Over the last few months we have been testing a number of improvements to how riders in groups behave in Zwift. These changes are now rolling out to all users and should result in improved pathing of riders in large packs. Users should also notice fewer instances where other riders appear to ride through the dirt or off road.