If you didnt want to go cold turkey there are a couple of options you could try:
1)start diluting down the 3am bottle over the period of a week or 2 e.g. instead of 6 scoops to 6 ounces start giving 5 scoops to 6 ounces, 4 scoops to 6 ounces, etc until you are giving only water. Your lo may be less interested in waking for a bottle if it is just water
2) start cutting down the amount you offer over the same time period e.g. offer 6 ounces, then 5 ounces, then 4 ounces, etc until you are offering only an ounce or two and then you could stop offering completely.
These 2 methods give your lo a chance to catch up on the missed calories during the day rather then leaving him totally starving in the night.
hope you find something that works for you
Seona