Hi - I don't think a 5 gallon tank is big enough to put too many more fish in, to be honest. Putting too many in that small area of tank space could end up causing more problems with bullying than you have already.
Also, if you did put a couple of females in there and they had fry, don't bank on all the fry getting eaten - I have a tank with two adult platies, an adult molly, a female betta and a red tailed black shark - when the platies had a batch of fry a while back, 10 of them survived and are now about an inch in length and I've had to re-house some of them into other tanks! There are also 3 slightly smaller fry that survived a more recent batch. Now, you'd think with those 4 other adult fish in the tank that no fry would survive!
Athena