We currently have 55 members which was recently cut down from 86.
Smart move. Many players who are searching for a CC will not join one with a lot of "dead weight", so that should help you attract more active players.
Unfortunately, there are many members we never hear from on Mobile Chat or on our Club's Forum so we can't really communicate.
As the Owner of your club, you have an option to EMAIL MEMBERS from this web site. It's under CLUB TOOLS. You can also go into OWNER TOOLS there and give that permission to other members (e.g. Directors). Granted, that only gives you one-way communication, but it's something.
We would like to be able to retain more experienced players who seem to join, look around and then leave.
There's nothing you can do about that. Club membership is a mutual thing. Every player has different things they're looking for from a club. This is even more true for experienced players. If your club appeals to them, they'll stay. If it doesn't, they'll leave. Similarly, if you don't want a player to be part of your club for whatever reason, you can remove them.
All you can do is set the table. You can't make anyone come to the buffet. It sounds like you are good at making your club's Guidelines & Expectations clear to your members. The ones who stay will be on board with those. Those are the ones you want to keep.
Ask yourself this: Would you really want someone to stay in your club if they're not happy there, or if they're not going to adhere to your Guidelines & Expectations?
Good luck with your club!