Now that Delta is all in Terminal A, you will almost certainly be able to skip security for a transfer. I think the 30 min layover is do-able, but it would certainly be tight. They have special carts for whisking you tight connection folks from the landing gate to the departing gate. That being said, the Song flights have generally begun boarding up to 30 mins ahead of flight time, which would mean that you'd be last on the plane, if you even made it.
But before you go changing flights: How long out is your flight? It is entirely likely that there will be additional schedule changes, which might make your layover in Boston longer, and a lot less tight. If your flight is within the next month, then you should change flights to get a more reasonable connection. If your flight is in, say, April you should hang tight and wait to see how the flight times change.
edited to add:(I notice now that your flight is Nov 30. Wow, that's close! yeah, you have better get talking to Delta and see if they can't get you a better connection. Even if you make it, your luggage likely will not with only 30 mins)
As for the ADHD issue, I would expect waiting in the airport would be preferable to running frantically thru the airport. And tho 90 mins seems long, remember that for the first 15 mins you are likely deplaning from your BGR-BOS flight, it'll take you at least 15 mins to get to the Song gate for the BOS-MCO flight, and they will start boarding the Song flight 30 minutes prior to scheduled takeoff in all likelihood. That leaves you a whopping 30 mins to kill buying drinks, using the rest room, maybe window shopping on your way to the gate. An hour and a half is an excellent connection for Terminal A in Boston.
Good luck!
(also I love the Bangor airport: huge runways, nice manageable terminal, in the heart of my Home State... sigh)