You don't have to have a Phosphate kit, but they can be helpful. If you do get one, I'd recommend the SeaChem Phosphate kit as it's easy to read, supposed to be nearly as accurate as the LaMotte kit, and comes with its own reference solution for calibration. Make sure to calibrate any kit that you base your dosing on, that way you can compensate for any error in the test results.
Bubble counters are nice to have since they allow you to check the amount of CO2 being injected with just a glance, but they aren't required. For DIY CO2 it is a good idea to have a gas separation bottle, which can double as a bubble counter. These will capture any junk that gets out of the CO2 generation bottles instead of letting it get into the tank.
Both sound like viable options, though I suspect those waterpumps you linked to won't have enough power for your application. I'd wait for someone who's more familiar with the amount of flow needed for larger tanks to chime in though.
There are water pumps that can be placed outside of the tank, but unfortunately they tend to be more expensive.