1) What size jigs? With a 1 oz jig, 64 tops, 1/2 oz, double that.
2) What size jar? I've got some 1 gallon jars that I've had for years.
3) Don't know, not done enough plastic baits to determine that one.
The do it molds site has some info on pouring jigs that you should check out. Will at least give you the basics on how its done correctly and safely.
Andrew