Well... not sure where to begin.
He put the fish in, so what’s done is done. He’ll be rehoming them (or cleaning up the carcasses) pretty soon once the fighting starts.
Inch per gallon is basically only applicable for small fish like tetras, and even then it is dependent on various factors. With large cichlids, it is just turning the tank into a boxing ring, and then a prison.
The 37 gallon African tank could work if he dropped the venustus, assuming the jewels don’t kill everyone. Having a 36 gallon mbuna tank though, all I can say is I wish I did something else or used a bigger tank.
The 10 gallon is nice and all, until the mbuna gets too big and needs rehoming.
And the 40... that’s good to know he has a tank suitable for the cories and the molly long term. My question is what happens when the Oscar gets 4+ inches, which will be in maybe 2-3 months, the frontosa will just die from the likely 6-7 ph generated from this level of overstocking, the bichir will get a taste for those small fish, likely a common pleco is at least half of that waste buildup, and parrot+angel+silver dollars are just the nail in the coffin. Not that everything else is fine, but this is just a bit of extra waste that makes the tank not even suitable as a grow out.
In all of these tanks, especially the 40, the fish are simply too much for the tank, especially a day old one as such. The little bacteria there is will be simply unable to ever keep up.
To help the cycle, he will have to either rehome all of the fish and wait for it to cycle, or continue with the massive water changes until it does. First one is a safer option.
I encourage the poster to keep up his love for fishkeeping, but rehome most of all of these fish, and greatly research the needs of the individual fish in his possession. If housed improperly, it is no fun for you and the fish. If done correctly, the hobby gives back just as much as you give.
I would say move the mbunas to the 40 and get a few more (once cycled)
Drop everything currently in the 40.
Leave the 37 as a tank for the jewel pair and some dithers.
The can be a qt/hospital tank.