Hi, I recently brought my 8 mths old baby to Bintan and to answer your questions:
1) Yes, you can bring food on the ferry and into Bintan.
Do note tap water there is not drinkable for both adults and baby. We had to bring 4 bottles of boiled water just for her formula milk and cereal. We drank the bottled water from hotel. Stayed at montigo resorts. Did think of bringing slow cooker, but was too much to bring. Hence we fed her bottled food and cereal.