Two month old twins!!

Twin Mom
Omg. It's hard! Like really hard. FTM here and now I'm an instant Mom of two. I have a couple of questions hopefully another twin mom or mom of two can help! 
They are still eating every 2-3 hours,  and taking 2-4 ounces. Is this normal? They are doing well for percentages (weight/height- heads are a bit in the higher percentile). DR says 4 oz every two hours is too much but they cry for more at times, and less at others. They started as preemies and are now average size which we are so proud but I also don't want to over feed. They say you can't but their dr seemed to think it's too much?
They only sleep 2-3 hours, sometimes less and randomly 4-5 hour. When will they start sleeping more???? Also, they have reflux and a mild case of colic. I know the colic should dissipate around four months- will they sleep longer then?
How do I do tummy time to avoid their tiny flat spots from getting worse? With two babies? They both have tiny flat spots on the back of their heads from sleeping on their backs:( I don't want them to get worse. I bought a baby carrier but I can only wear one baby at a time. The rest of the time they are asleep. 
When they both wake up to eat I have to rush to heat bottles (DH preps them and sets them up in the fridge for me) and rush to change them both- someone is always crying! I try to hurry as I've read it's not good to not answer your babies cries. Ughhh. I'm trying:( it's overwhelming. BTW they need formula due to allergies though I'm still pumping to maintain my supply. 
While my DH works, I'm the SAHM. Basically I work 18-20 hours a day taking care of the twins. Non stop. I'm exhausted. Maybe I shower every three days. We live far from friends or family so no one can help. People want to visit the babies but that's more for them to have fun, not to help us. Hiring a nanny to help me isn't exactly in our budget:(
Any answers to my questions or advice would be incredibly appreciated!