Are there any positives to having dyslexia, and how can you tell if you have it?

Not sure: I've never heard anyone describe positives of having dyslexia. Think of it more as as a part of the brain that, from an evolutionary perspective, has been required only relatively recently, so lots of people functioned just fine in the past without needing to read but it's much harder to do so now. There are effective treatment interventions. Look up slingerland & lindamood bell, among others.