The only logical conclusion I can accept is I screwed myself over
I would not beat yourself up over this, chris. You were up against an attorney who was probably experienced in landlord/tenant issues. Very few pro se's can out-lawyer a lawyer.
Even if you had done everything absolutely right, you would probably not have won the case because oral agreements are hard to prove - and the landlord relied on his written lease agreement with you to support the fact that you left before your lease term was up. If you had a document signed by the landlord agreeing to release you from the lease early, then THAT could have changed the decision to one in your favor.
And, again, the bedbug issue is a tricky one in all states that have heard cases involving them. Their source is often impossible to prove, and eliminating them from a property once that property has become infested is also nearly impossible. The landlord, however, did attempt to eradicate the bedbugs with four treatments, which showed he addressed your concerns, even if the problem was not resolved.
I suggest in the future that you carefully inspect the unit you will be renting and investigate the history of the landlord (i.e., any court actions taken against him/her) prior to renting. This won't tell you everything but it can tell you a lot.
Good luck.