As far as the new tools making a design premium, that's unfortunately how it's currently set up.
(As an aside, your Underworld watchface will probably get flagged for copyright, as it's a premium design and not allowed)
Premium is a subscription that runs $4.99 a month, which gives you access all the premium faces people have made. It's a balancing act deciding which designs work as free and which need those extra features (themes, etc) It's a fairly new offering so I think everyone's still figuring things out. Opening the tools to more people means more new innovative designs possibly. So, I wouldn't worry about being annoying per se, but you should try to made the best designs you can. I think your Dashboard design is awesome, you nailed the red LED look and already got a handle on doing a speedometer/hour indicator.
As far as making 2 versions, a lot of designers do that, one with the features and one without. A lot of times they'll release a watchface and feedback is given where people want the design, but in blue/etc. Again, keep in mind people have to pay to access the premium faces and unless its really unique/awesome there may be a free version out there already made.
Sync data? On the design page it lists your own syncs as well. I'm not sure the exact formula but I think it might be hourly. It's still being tweaked since it was only showing the faces sold, now it includes premium designs. Either way, I don't think you could sync your watch 1000 times and climb the charts that way. You can check on the stats page in the editor (https://www.facer.io/creator/insights) and maybe find out more data that way.
Hope this helps!