I'll applaud your description of the wards and how they were supposed to work. Given that they're not working, I can't blame Harry for cutting the connection, he certainly doesn't owe them anything and a stronger him, there, will be more protection than those failing wards, anyway. I'll agree with Alorkin that this is more an efficieny question than one of ruthlessness. I do wonder, though, if Dumbles has a monitor on the wards? If he does, it might not notice when Harry severed the connection, but it most certainly will when the wards on 4 Privet Drive fall. This could provoke an early encounter/confrontation with the manipulative old bearded one.
I do like the systematic approach Harry's taking to exploring his magic, it's a most logical and scientific one and I suspect he's going to find a few things that a lot of folks would wish he wouldn't.
Author's response
I plan to have the wards last about three years before they completely fall. There will be an early confrontation though. It will have nothing to do with the wards however. You'll just have to wait and see. As for the efficiency versus ruthlessness, like I said in my FFN profile, Harry will be dealing with using what he knows with ruthless efficiency. So I guess the question becomes rather moot.