Sounds like you have taken it pretty easy on your method of camping and never needed any more. That works in your favor if you are going to extend your trips. In short, yes your TV will recharge your trailer as you drive if the lead to your battery from the 7 pin plug is live. You will only be charging a few (5-10) Amps at best.Batteries charge quickly to about 75% -85% charge, but to get the final top off go very slowly. your battery is likely holding about 85 amphrs total capability. To recharge fully would take a full day of driving. If your trailer has space to add a second battery, that would be a good first step, A generator to recharge and let you run other items would obviously help too, you could also add a solar panel to trickle charge the batteries to extend their operation, this has the added benefit of keeping them topped off when the trailer is not in use.
There are many threads on here giving the technical information on how to measure usage and determining drain on your batteries, Read a few, try using a voltmeter on your next trip to see how much you are runnoing the battery down and then you can figure out what you want or need to get what you want from your setup.