Alert Rules Priority Value Duplicates

Yeah, it doesn't hurt anything unless an alert matches 2 rules with the same priority. Then there's no telling which rule will route the alert. 

Limit - do you mean the Escalation Chain's rate limit? You can bump it up to 1000. I have that on several of my chains where I don't ever want it rate limited. I'm not sure how it would impact the current alerts. Alerts that weren't sent out should be queued up, so raising the limit should allow queued notifications to go out.