A bottle of formula isn't going to make a difference. Your milk is higher in fat nad will satisfy him just fine. I wouldn't even bother with formula.
Each child is different. my oldest slept 7hrs straight from 5wks old. My youngest woke twice at night to nurse until 10 months old! We never did cry it out, but at 10 months my husband would go in when he woke at 3am and pat his back, give him his blankie, and 'shhhh' him for a bit. He was ok after a day or two, and shortly after gave up the 5am nursing too and started sleeping until 7am.
Also, I nursed both my boys to sleep from birth until we weaned close to 2, and neither had a problem sleeping by themselves, so if you are nursing him to sleep, don't worry about that. It never ever affected either of thier sleeping habits to nurse to sleep.
But have dad go in at night and soothe him. Have him give him a blankie, his lovey, a pacifier, whatever he uses as a lovey. Have him pat his back or rub his tummy and soothe him, shhhh him. Keep the lights off, keep it calm and mellow. My youngest was (and still is) infatuated with this Glo E Bear. Its white, can get a small one at Target for $12. It lights up in different colors, awesome. He would go in, turn that on, and my son would stare at it and drift right back to sleep. IT turns off automatically after 15 mins. Its a neat little thing.
But having your husband go in will make the difference. Give him a few minutes, then send dad in to soothe, then wait a few more minutes, then send dad in again. HE'll get it, it'll take a fw days but it will work. :)
Congratulationso n the breastfeeding. :)