A., we had the exact same problems early on. I would highly suggest sticking with the Similac Sensitive since it works for the spitup but add 1 drop of Mylicon (or generic gas drops work just as well) for each ounce of formula and shake it up in the bottle with it. This worked WONDERS for my little ones gas issues. I tried giving her the gas drops straight as a single dose but it didn't do anything to help with the gas, so on the suggestion of a friend of mine I put them directly in the bottle and it was like night and day. I also like that this way she was getting a much lower dose of the gas drops than if I'd have been giving them directly with each bottle.
She still got some gas from the formula but the gas drops made the gas just move through her so instead of it backing up and making her miserable, she just tooted a lot and seemed fine. As she got older and the gas wasn't as bad I reduced the drops to 1 drop every 2 oz of formula. Now that she is 22m old I still occasionally put a few drops in her nightly milk if she's had something for dinner that I suspect might give her gas.