Is there a difference in pronunciation between "ist" -be (3p. sing) and "isst" -eat (3p. sing)?
EDIT: I posted the second part as an independent question
Actually no, but lots of Germans pronounce "ist" without the "t" at the end.Generally there is absolutely no difference. You can guess the meaning from the context like
Er ist/isst ein Kind.
Here it is clear that it has to be "ist".
Er ist/isst eine Suppe.
Now it is "isst", because usually you can't be a soup :D
In "isst", you put more emphasis on the i and the s is a little bit sharper than in "ist".