You sound like you have a good idea of what went wrong. But surely you got a lot of things right too. What were they?
It would sound like your mistakes point to a lack of research. It sounds like your co-founder isn't a friend, so you didn't know enough about him to get started with.
Finally, this isn't legal advice, but don't give up on the trademark situation yet. Especially if you haven't launched. I'm not so sure the other party would be willing to pay lawyers for a lawsuit, especially onsidering there isn't much to get out of small bootstrapped startup. Also, if you haven't launched, then you dont have very much to lose. You haven't established a brand yet, so perhaps this might be the best time to tweak with this. And of course, you'd want to improve on your branding research this time.
It would sound like your mistakes point to a lack of research. It sounds like your co-founder isn't a friend, so you didn't know enough about him to get started with.
Finally, this isn't legal advice, but don't give up on the trademark situation yet. Especially if you haven't launched. I'm not so sure the other party would be willing to pay lawyers for a lawsuit, especially onsidering there isn't much to get out of small bootstrapped startup. Also, if you haven't launched, then you dont have very much to lose. You haven't established a brand yet, so perhaps this might be the best time to tweak with this. And of course, you'd want to improve on your branding research this time.