Is this normal for a 9 month old?

*Please no judgment, I only ask because I am very cautious of the care of my baby*

My son just turned 9 months old yesterday and had his 9 month checkup today. They said they wanted to watch his growth because he’s only gained 1 lb in 3 months (he only weighs 16lbs) and hasn’t gotten any taller since his last visit in November. They said I look small too so they are just assuming he got a good metabolism from me. To help bill him up they said it might be helpful to give him smaller amounts more often. But then they said that he should only be getting a MAXIMUM of 20 oz (we formula feed) a day and to give it in 6 oz increments. Then the rest of the day we should be giving him rice and meat to fill him up. So we are supposed to only give him 3 1/2-ish bottles a day and then rely on rice and meat. Which I wouldn’t be too hesitant about if I haven’t always heard that babies under 1 should still rely on formula/BM for all their nutrients. They also asked if he still wakes through the night and I told them yes. To which they said that he still wakes up through the night because I taught him that if he wants to eat at night, i will give him his formula and that we should let him cry when he wakes up hungry.