Some quick answers to your questions-
1. If you get some sort of USB gamepad controller, you can plug it into your laptop and use it to control the ROV, but if you don't want to use one (or don't have one) you can also just control the ROV using your computer's keyboard. The nice thing about using a gamepad controller is that it gives you proportional throttle control.
2. The tether plugs into a small box (which you build as part of the kit) called a Topside Adapter. This box converts the twisted pair tether back into regular Ethernet that can be plugged into the Ethernet port on your computer. The box also needs to be powered by something, so we've made a plug that supplies voltage to the topside adapter from a USB port.
3. If you have a wireless router, you can plug the ROV (via the Topside Adapter) into that and log into your ROV wirelessly. There is currently a little bit of work being done to make OpenROV Cockpit (the interface for the ROV that you pull up through your web browser) work with keyboard-less devises like smartphones and tablets, but that's still a work in progress.
We're always looking for help with development, so even if you're not super tech savy, we'll be very interested to hear any ideas you have for how we can make OpenROV a better tool for field work.
It sounds like you're doing some pretty cool stuff- any job that involves being out and about is the right kind of job to have!
I hope this helps,