Hi, I'm new and need a lot of HELP!

You seem to have it mostly right. The Tx rates control how fast you roll, making things more or less responsive. The FC has limits on the roll - unless you're in acro mode - and you can't change those without reprogramming the FC. Roll determines how fast the quad moves in the direction it's rolled toward, and the tx rates determine how fast you roll.

The Nano QX 3d stick behavior is pretty much standard. That's what the 200QX does in 3d mode, and what collective pitch copters do. I know some of the 3d toys re-arrange everything when in 3d mode (though I'm unclear on how some of that can work as described). Yes, you could set up a mode on your Tx to have the throttle go from 0 to 100 (scale 50, offset 50). The possibility that you couldn't descend with the Tx in that mode and the quad in not-3d mode worries me enough that I wouldn't do it, though.

You can definitely do what you're describing in devo, not sure anything about the nano qx 3D though...

Take a look how I do 3D mode in devo with cleanflight.

My inputs to attempting to eliminate the engine reverse for the nano 3D in agility mode:
-Mike advises not since the toy FC's aren't transparent as say a Cleanflight implementation - no telling what will happen
-CK says it's "very very complex" (but I think he has got the 2D/3D capability I want - just don't know if it would work with this toy FC)
-I took the working model I got and tried to mod it using the transmitter screen (adding min=0, max=100 on the throttle, as well as scalar and offset of 50). It revs for about a second, then shuts down and doesn't respond to the throttle in any switch mode combination (HOLD and FMODE). Strangely the emulator shows CH 1 at 100% when throttle is at 100% in any switch mode combo. Before mods FMODE1 was throttle cutoff (-100%).
-I finally looked at the program that resulted from my mods, and it was a "simple" template with no switch, so I don't know how that could have worked anyway. At least the emulator response (+100% constant) was understandable, even if no response to 100% throttle was not.
-I'm tempted to try to modify the model programmatically instead of using the transmitter, but I don't know my way around the block yet. There are commands in the program that I can't find in the User Manual. I do want to learn to write scripts at some point.
-I've read several posts from Nano fanboys on RCG that are not fans of the Nano QX 3D, especially the agility mode behavior.
-I think the quad is also having some hardware issues, possibly motor going out and it can't hold on to its props. Not sure I want to fix it.

So, I'm going to put it down for a while and move on to some higher priority projects. First up is my DEVO 7E mods and multi-module build.

Thanks all for the support so far.