Honest opinion bin the smart valves / trvs and just use the trvs as over temp room control
Wc and timer that’s it you can go dumb eg lifestyle 111 or still dumb but internet controlled eg nest let the wc sort the temp out might take a...
What system is it going onto eg rads ufh etc
At a min I would weather comp but be warned are they used to hot rads when they turn the heating on as let’s say October time they would be lukewarm due to warmer temps etc
You are turning the right way ? I only ask as it will only turn one way the lever / handle has stops if you look you will see it hard against the closed one
Worst comes to the worst undo the screw that holds the handle on little pozi...
If it is a condensing boiler the line will need to be replaced back to where it connects to the main stack hope this is cast and not copper
I suggest you make access as it could be leaking where you can’t see and causing damage