The tank bottom does not have enough area with the Raphael cat to support a school of Cory cats. Rams might work as they are also cichlids and can, most of the time, stand up to angels. You already have found out your angels are aggressive and in order to add new fish your best bet is to remove them from the tank, put them in a bucket for a short time, and re-arrange the tank. I know you have limited options in a 40 Hex but since the angels have claimed the tank as it is as "their" territory it needs to be changed so it's a new territory they aren't familiar with. After changing the scape, add the new fish, let them settle, then re-add your angels. This is your best bet for adding any new fish. If you add new fish, just about any species, you are most likely going to have a repeat of the rummy's. This wouldn't be an issue if they were small (nickel size body or smaller) but since they are mature adults and they have not had tank mates other than bottom dwellers they think the tank is theirs and as is, not willing to share. Dwarf gourami's might work. As for low light plants, you tank is tall and a bit narrow, so you could use all types of anubia, some types can get tall, crypts, and I believe jungle val, which would grow to the top of the tank.