OK, looks like it is indeed 2A. It’s true that connecting three stations in parallel would be the easiest, as no software change is needed. But I have never tried running a 2A device so I can’t say definitely it will work or not. If you decide to try this out, also note that OSBo has a on-board 2A fuse, which you either need to upgrade or solder a wire across it to bypass it.
The relay is connected to pin P9.16. Writing a high to this pin will activate the relay and low will deactivate the relay. Using the relay does require some software modifications. Probably the easiest is to conceptually assign the relay to a specific station (say station 1). Then you just need to go into the software and find where stations are activated and deactivated, then add a couple of lines of code to wirte HIGH or LOW to P9.16 if the station index matches the pre-assigned station.