I usually give him 6 to 7 ounces of formula every 3 to 4 hours. Is that too much or too little?

At his age you shouldn't hold back if he's still hungry. His body self regulates if all is well. How is his weight percentile? Ours was always on the low side... he's a "string bean"... so we fed him as often as he wanted... and 6-8 ounces of breastmilk was common in this timeframe of 3-4 hours.

As you come on to 6 mo you can start considering supplementing formula with solids, such as rice cereal, if he is seeming to be still hungry after formula. We waited well past 6 mo for solids as we had an ample supply of breast milk stored in the freezer and wanted to use it as long as possible, but I think he wouldve gladly started solids sooner.

Does your child seem hungry all the time? Is there a problem or are you just asking?

My second Grandson is 3 months old. We introduced both boys (first Gbaby is now 2 1/2) the stage 1 and stage 2 baby foods OR rice cereal mixed with 4 oz of formula. They both tolerated it well and "feeding them" didn't change their bowels habits as it will constipate some babies. (baby stage 1 and 2 bananas is good to regulate that problem) It will satisfy them so they will sleep better and not want to eat every 2-3 hours. Keep in mind that every child is different and results will vary...
You can also pick up a Sassy Ceral/Food Feeder at your local CVS. It's excellent for stage 1 and 2 baby foods.
Best of luck to you

Sugar water and Sweetened Cat Nip Tea (buy @ local health foods store) are wonderful in addition to formula and stage 1 and 2 baby foods.