S.M.
There are toddler toothpastes available w/o fluoride (Gerber is one). You only need a pea sized amount of t.p. on the brush.
If you do start using fluoride t.p., then just watch him close and stick to a timy amount of paste. My son is 3, and he swallows it most of the time. Have never had a problem.
Important to try to get floss in between his teeth, too. If he will let you, the little floss piks work well.
Soda is the worst thing for teeth (sugars and acids). Try to only give a little on very rare occasions!