Two things:
- EssentialCmds is now discontinued, and you should move to another Essentials like plugin. I am completely biased and would recommend Nucleus (which I write) which is a kind of successor of EssCmds, and has an migrator that you can use to move to it from EssCmds, but there are other alternatives in the works, such as UltimateCore and CrucialCraft. You should pick one that fits your needs - other members of the community should also be able to advise you.
- You have your parents the wrong way around -
Mod+should haveModas a parent, not the other way around (where you have Mod+ as a parent of Mod). A group inherits all its permissions from its parent, not the other way around. So, right now, your Founder has no permissions, and your default group can do everything (because its parents go all the way up).