Depends on how many rounds you are adding. If +2 stock spring is usually enough. To make sure, I always use Wolff +10% springs and have never had an issue.
If adding more than 2 rounds, check with the company you are buying the base pads from and see what they recommend.
Replace the control. R8184G 4009 Should stop the issue. You can hear it dropping out. If it was the pump coupler the motor would continue to run but the flame would drop out.
When you change the control, change one wire or set of wires at a time to prevent screwing it up
Looks like the first floor is piped of the original black taco pump hidden in your pictures behind the exhaust vent. 2 pipes indicate a split first floor loop. Guessing the pump is bad or the internal relay inside the boiler is bad depending on how it was wired. (Many electricians screw this...
Plus, if it is built into the wall upgrade. Tub and Shower valves are a huge problem. Stay away from Delta, American Std, and Kohler. They don't last and don't repair easily down the road.
Hydro Air is a very good heat/cool system that allows AC down the road if you don't want it now. It...