Sexing is quite hard with these species. The only differences I could tell is by the shape of the head. The male wil have a slight angle/hump as to where the females are just straight or rounded. Pretty hard to see from the begging but it's there. It's slight as well.
As far as having 2 males in the same tank, it is possible but the fish they're being kept with must be twice the size and your meaner ones. Will also need to pack the hell out of the tank. I think in my 90g I had around 20 cichlids in there with 2 5 spots. You basically put so many fish in there so there' son territory to claim at all or there's to many for them to chase. This is the only method I've found to be successful with pairing these guys.
All cichlids I've put in with these guys that were the same size, all have died. Didn't matter what they were from RD's, Dovii's, you name it. they must be bigger. These guys seem to grow pretty quickly to 6-7" so they've out grown all the cichlids I've put there with them. I've made a network in my area and we swap bigger cichlids around when trying to pair these guys. So for a 3" fry, we have a 7" RD, 8-9" Oscar, 7' GT, a 6-7" umbee and a few others. When things get feisty, we load the bigger ones to each other.
Get more side shots if you can. I'm thinking this one with the bite on the head is a male.
And just because it's the dominant one doesn't mean it's a male. I've had some real nasty females killing all.
This vid is one of my F1 fry, started flexing as soon as I put it in with my big boys. I though this was a male, it ended up being a female.