I've done this by pricing the app at zero dollars and implementing an IAP for whatever you want the subscription to be. That means you have to put in the free trial period code that saves initial install date and times out after the trial period ends and disabling the app after the trial period ends.

I have the reconnect issue too, but I’ve found that restarting the Mac allows the reconnect to occur. Although the reconnect issue reoccurs pretty quickly . I try to do as much as possible using a simulator before using a live watch. I’m making progress with my watchOS app development but it’s still a pain.