New cat question & weight question

Hi all. I am finally getting a new cat on Sunday from a shelter. I took my
Randi to the vet for shots yesterday. They said he is
too fat - 15.75 lbs! And that he has a very slight heart murmur, which is
more reason to make him lose some weight.
It was hard when Elvis was here to distinguish who was eating what, but now
it appears Randi is eating 2 or 2-1/2 3 oz. cans a day and very little dry
food. The vet said to cut him down to one small can a day and two cups of
dry. But he doesn't eat that much dry food.
How much do your cats eat? He is a big cat, not just fat.

When I get the new cat (an adult female) after I take her to the vet right
away for bloodwork, when she gets the clear and I can bring her home, I need
some suggestions for introducing them to each other. With Randi, he was
only 9 weeks old and Elvis was mad at me for a day and then he mothered him.
I kept Randi in a separate room for a couple days and then they were fine.
Just would like to get
your suggestions. Thanks, Carol Oh, and my vet has KITTENS available
in a couple weeks! They aren't ready yet but
I think I am going to get two. Or three. lol