Shower Repair Advice Needed

Manufacturer is Delta. It has a single knob to control water temperature, a push button diverter just below the knob, and a spout down below.

I was having an issue with the diverter. It wouldn't stay pushed in, or it would push in, but half the water would still come out of the spout. I got a new push button diverter and was going to replace it. I unscrewed the screw from the center of the knob, but the knob doesn't seem to want to come off. So I thought I'd just use a wrench and unscrew the dome that's behind it to get that off anyway. One slight turn took a little force, and I decided that this isn't a project for 8pm Sunday night, and I'm not interested in being showerless to start the week. So I turned it back.

However, now it's leaking a little hot water. The leak is coming from the bottom of the spout, where it meets the wall. I turned off the hot water, and the leak is stopped. So 2 questions:

1. Is that leak an issue with the spout, or did I more likely disrupt the knob, which is now not fully shutting off the hot water, or both?

2. Would a spout with a diverter work in this system, even though there is a push button diverter? For future issues, I'd much rather pop on and off a new spout than deal with the knob and all that's behind it. But I don't know if that even physically works. The pipes behind my shower are the last old copper I have in the house, so the less I can disrupt it, the better.

Thanks for the help!

the handle should pull off aftr screw is removed,,pull it like you mean it.

then remove face plate...then post picture of what you find

You have to pull the handle off. If it's really stuck, a faucet handle puller tool makes it easy - search on that, or for example, see:
http://www.lowes.com/pd_120988-943-03875_0__?productId=3136255

When you get the handle off, you should see a plastic ring under the metal dome, with two slots at 180 degrees. You probably loosened that when you loosened the dome. You just tighten the ring to stop leaks. There's also a special tool for that

Be sure to turn off the water before removing the dome, but if yours is like mine, you do not need to remove the dome (or even turn off the water) to replace the diverter. But you do need to remove the face plate. Then you may need a deep socket to remove the diverter.