Milk drying up .. need gudiance on formula feeding

My milk is drying up after 1 month :( so I need some gudiance on formula feeding

1. Can I prepare bottles and put in the fridge and warm them up when he needs to feed?

2. How long can it stay in the fridge?

3. How long can it stay outside the fridge? (Let's say we ate out & not at home)

4. What to do when we not at home & he needs to feed?

5. After warming the bottle up how long can he feed from it?

Help me :(