Moving to a 4 hr feed routine and, thus, dropping a feed won't necessarily cause night wakings. As they age, babies' tummies can hold more, and if he can take 4x 8 oz bottles, then he'll still be getting 32 oz. Also, if you want to try dropping the catnap to see if that improves his early morning wakings, I think that's a good idea. Usually, baby will start refusing the catnap as an indication to drop it, but it's all trial and error. If you do drop it, try putting him to bed a little early for a while until he can adjust to missing that sleep. It will be hard for him to stay awake until bedtime at first dropping the catnap, but he will adjust. Or, you can try backing it up to only a 30 min nap, then 20, then dropping it.
As for solids, they aren't necessarily the answer to guaranteeing night sleep. Some babies' systems just aren't ready to handle food as it can constipate them and/or cause gas. Also, it takes them awhile to get rid of the tongue thrust/gag reflex and they don't usually swallow much of it at first anyway. Unless your ped advises solids early for medical reasons, I'd proceed with caution.