Milk is the most important nutrients until one it has everything that baby needs until one I would try to give some milk in a sippy cup. Maybe the bottle is overstimulating now
I think as long as he is eating a balanced meal of solids and drinking water, you should be fine!
My little guy has preferred solid food since 7 months. He takes between 4-12 oz a day. But he also loves water, so he gets fluids from that and we do lots of fruits and veggies. I say just continue to offer the formula throughout the day. If your Dr. isn’t concerned I would try and just cater to what your child wants.