Re: when you and DH disagree?
We don't co-sleep, never have. I'm also a very light sleeper and can't sleep with all the little baby noises. I'd also lie there awake convinced that one of us is going to roll over on the baby and smother him.
I think it's around 4 months or so when your supply is really well established and you don't feel "full" anymore. That doesn't mean your supply is low! It just means your body knows what it's doing and is tuned into your baby. As long as there are wet and poopy diapers and your LO is gaining weight, you're good! I do remember panicking though because I thought I wasn't producing anything for a while there.
As for herbs, I drink Mother's Milk Tea pretty regularly. At this point, it's really just because I like the taste. I also took Fenugreek for a while there and it did help, but it makes you smell like maple syrup. The thing that helps me the most is drinking a TON of water. And I mean a ton. You cannot drink too much.
I'd skip the formula if you can, at least for the first few months to get your supply going. And if you feel like you're failing, go find a friend or family member who has nursed or a lactation consultant to talk you off the ledge. You can do it!