Channel 1 doesn't really break up that way, at least not without some funny-looking settings. The gain definitely warms up the tone and as you've discovered, the treble also acts like (i.e., IS) another gain control. Read the manual again if you haven't, it breaks down the way the controls work very succinctly. Also, it's recommended that you forget whatever you think the gain and tone controls should look like and get familiar with how they work together. You should be able to get there.
Personally, I really like the way Ch1 breaks, and it's what I think of when I think of Fender-style breakup. What you describe sounds, to me, like a slightly more "British" style clean breakup (this is totally subjective, of course), which I think of as having more of a crisp top-end and more defined high-mids, with the lows very much in the background or at least not creating any mushy low harmonics of their own. If I were trying to get what I think I hear you saying, I'd start with the bass all the way down, gain at about 12:00 and work the treble and mid controls. Presence will usually smooth things out, so find a setting and then add or subtract presence to taste. Add bass to fill in the bottom end once you have the texture you want.
