I was wondering if I Auto bought with a different account than my main, on a different computer would affect my main account?
Yes. This is what is called a chain freezing. All TNT will do is look at the IP address and freeze any and all accounts related to the one that was autobuying. However, if you do get all yours accounts iced, you could email TNT and try to make the argument that the accounts are played on by different people and that you, the owner of your innocent main, were wrongfully iced because of something somebody else in your household did. It's a long shot, but if there is absolutely nothing that links the two accounts, then you just might have a chance of saving your main.
If you use a proxy on the account that you are ABing on, your main account is fine! (As long as you NEVER log into your main account while on your proxy)
Well just turn off the proxy when you want to log onto your main account and then turn it back on when you're ABing, quite simple
Just use a proxy every time you access/use a program which accesses an account besides your main, and use your home IP for your main. And btw public proxies will pretty much be useless..you'll need to buy some if want reliable ones.