The 7d isn't much of an improvement in low light, snapsort compares the two as:
I believe they get the results from dxOmark, either way I've heard it's not a great deal better.
the t2i is dirt cheap, you can get them for $300 without much trouble, the 7d is what, a grand roughly? if you end up breaking your t2i because it's made of plastic and not metal, and I very much doubt you will, just buy another, I've had my t2i covered in snow, relatively wet powder got in the hotshoe, the jacks and all over the screen and body in general. It then ended up melting and refreezing, it was still working perfectly after. Refer to earlier in this paragraph.
Is the Autofocus on the t2i holding you back? when you say better, do you mean faster, more accurate etc? what lenses are you using such that the camera is holding you back.
Burst, and more importantly the buffer, is far better on the 7d, but I highly doubt you'll be glad you upgraded for exclusively this.
As for a better sensor, I believe it's got the same sensor as the t2i, not definitely, but if not it's definitely close from what I've heard/seen.
Are you being a bitch? most likely yes, but everybody does it, especially me.
Post up some photos that you have been unable to use due to your body, I doubt you'll have any that would have been usable with the 7d.
Also I presume you're wanting to stick to canon?