AFAIK yes they're standardized, even though most connectors you see in the field are NOT actually from Molex, but clones (and I have no idea if they're "licenced" or not; I would assume "not"). That tool looks about right from what I've seen other people use (I've always just used pliers), and you would just need more connectors. If you're just trying to add connectors, I know that back in the day you could get "snap-on" 4-pin connectors that had "blades" on the contact side and would just pierce the wire's insulation when you clicked them on. You may or may not be able to find those today. If you're going to make y-splits (well even if you go with snap-ons actually) make sure you aren't overloading the wire itself with current draw.