I was of the opinion that milk is the most important thing in the first year and that food is for fun!
You are totally right! 4 bottles a day is perfectly normal for a 7mo, in fact some are still on 5. It is recommended to go down to 3 feeds/day at about 10 months or give or take.
I'm not sure where you live - in some countries they rush solids more than others. I'm in the Netherlands, and here they are quick to get into solids and recommend doing 3 meals a day with the 2 bottles and sippy of milk that your nurse mentioned by 7-8 months. I did not listen to that advice, because really formula/breast milk really supply way more vitamins and rich nutrients at this age than solids do. The solids at 7 mo are to get your lo used to eating these foods.
As for the sippy, it is not a bad idea to offer a sippy during the day. But until he is adept at drinking out of the sippy, I would just fill it with water. It will be frustrating for you both if he wants his milk but can't get it because he can't really navigate the sippy, kwim?
Sounds like you are doing a good job and his meals sound fine too. At a certain point you can introduce more foods at lunch between bottles if you want such as strips of bread, rice cakes, veggies, etc.
