A little advice, having kept both and also as my first fishes. I think you're fine for life in that 55. Your Dempsy's might pair off or might not. Obviously they are too small to sex now. But Blood Parrots are interesting fish. They posses the prowess of a midas, but given their deformed mouths, and chuck body they at best might headbutt a tank mate. Dempsy's look nothing like BP's so aggression between them should be a minimal amount.
The biggest issue I see arising in time is your lack of filtration. I would recommending adding either an Aqua Clear 110 or two Fluval C4's. If you opt for a Canister, look for sales. Pet-Smart which is never a first option has 2 big sales each year on the Fluval 306 Canister Filter. It goes on sale for 70.00 which is like 50% off. Black Friday and usually a new years sale. So keep an eye out. Otherwise get a beefy Hang on the back. I also would just remove an air stone, and add that air line to a sponge filter. Just for the add bio.
Light time is entirely up to you bud. You wanna use a razor blade and keep you class nice, run it longer, personally I run mine like 6 hours a day. My planted nano runs 12 hours and has zero algae so it's really dependant on each tank and it's inhabitants. BUT! Do not let natural light beam in to the tank or you will get big ole algae blooms.
GL Man.