It's a balance, and more likely trademark than copyright (unless there's art on the shirts). As you correctly point out, you don't want buyers to...

That sounds like the 50 year old myth about mailing it to yourself. Since 1978 if your work is "fixed in a tangible medium of expression" you have...

That's not really a question. If you're wondering what remedies you might have, the first place to look is your contract with Instagram. Might be...

Good answer above. When someone says they "change[d] the design slightly" or "followed the 10% rule" they are probably indicating they don't know...

One would think that for a project as advanced as you describe, there are contracts. That is the first place to look. If we assume there are no...

There sounds like there is significant risk. Avvo isn't a place to get legal advice about specific situations. The standard for trademark...

It's hard to see how that would not be infringing, unless you only use historical characters whose copyright has expired.

A defense lawyer would know how to address the issue of authenticity of the photos.

Retain your own lawyer. Avvo isn't a place for legal advice about specific situations. Consequences from trafficking counterfeits can be...

Chances are good you can't get a "clearance" on Avvo. This isn't the place to answer specific questions, and you wouldn't want legal adice to you...