You can give colief straight into the mouth before every feed, or during the feed if the baby is happy to come off.
It's extremely difficult to get into a good routine with a refluxy baby. Some babies can be unsettled, miserable, bad sleepers, poor feeders because of lack of routine, but lack of routine does not cause reflux.
A 9w baby crying every evening is classic for colic, and it's true that he will grow out of it. Doesn't make you feel any better while he is crying, though! Again, slinging him may help. Please don't worry that it will become a habit that you can't change. Any habit or routine can be changed when it's no longer needed.
Colic can be caused by lactose intolerance. I think. I don't know whether this is still current thought.
I'm not saying that all his problems are caused by lactose intolerance, or that colief is the cure-all. But isn't it better to try something mild before going on to prescription medication?
I wouldn't restrict his daytime sleep right now. He needs any sleep he can get. Even if he ends up sleeping more in the day than in the night, if he is more settled and you can cope with the broken nights (nap when he does?) then, again, it's a routine that can be modified when things are better.
One other thing, your own diet. Reflux can be connected to cows-milk protein intolerance, and a very sensitive baby can be affe ted by dairy in their mother's diet. Would you consider going strictly dairy-free for a month to see whether it has any effect on your ds?