You guys are right. Main shut off and hot water shut off for 1 hr, the water still trickles at the lowest point. So the master bath tub faucet (on ground floor) and outside hose spigot still runs. When I shut those off, then the kitchen faucet starts to trickle. I think the main shut off needs to be replaced.
I'm also giving up on putting in the rest of the 11 shut-off valves with Dahl. They aren't actively leaking, the green deposits seem to be doing a good job, and I'm terrified of further damaging all these copper pipes with changing valves so many times. If/when they start leaking, I'll have them changed out with Dahl but will not be proactively doing it. See all the trouble that got me so far... Will be emailing Supply House / Dahl to see what's the shelf life for all these Dahl valves. I might want to return some of them.
Will be contacting a few recommended plumbers this week to change out the main shut off from gate valve to quarter turn. And have the plumber snip off end of the kitchen faucet cold water copper pipe that's deformed where the valve is still leaking (very slow, no water in the bucket overnight but wet).
Will be checking the valves periodically to see if they're leaking. Luckily, if they are, it seems to be very, very slow, like a drop a day. Bad decision 5 yrs ago to use the Home Depot Brasscraft valves so gotta deal with them now. Live & learn.