London Heathrow to New York JFK with connecting flight from term 8 question

I'm flying home for a visit!!!! Yayyyyy

So I'm flying from Heathrow to JFK to Pittsburgh

Will be landing at terminal 7 and my connecting flight is from terminal 8. Will I encounter a second security check at terminal 8? If so, will we be streamed in with all departures in term 8 or will those with connections have their own lines.

Also, will be taking my mamas and papas stroller. Will i have to take the seat off to fit through security? Although you can fold with the seat, should I get 2 gate tags just in case? Do you think the stroller is too big? Think it weighs 24 pounds total. Not worried about it getting damaged, bought it preloved.

And finally...my baby will have just turned 1 when we fly out and is on special formula bt prescription. I will need to take 6 900g tins to cover the 5 weeks 2 days that I will be there. Should I check it in or carry it on?

Sorry for so many questions but just looking to make our travels easier by knowing what to expect

Thank you all!

I would only bring one in your carryon and pack the rest in checked bags.  I don't know about the connecting flights unfortunately.  Think we had to carry Thomas (13 mos) through and fold his pushchair so it could be x rayed (but we just had a small umbrella one).

I don't have any answers, but I hope you have a great time! I just got back from Pittsburgh, visiting my parents. We actually flew Heathrow to JFK, too, but then rented a car and drove. 

Hit up Primanti's for me. And take your baby to Kennywood!