Ok, so lets try to help you get on the right track.
First off, you are feeding too much. You have 2 clowns, a firefish, a pj cardinal, a yellow tailed blue damsel, and a royal gramma. All of them are herbivores. What do you feed? I'm personally a fan of frozen foods, specifically mysis shrimp and blood worms. I feed my tank half a cube twice a week after rinsing off the food once it has thawed. So basically, you are feeding too much.
In terms of cleaning your tank, it sounds quite similar to what I am doing. Yeah, it sucks cleaning the sponges I won't lie. But cleaning them weekly will aid you avoid issues later.
That thing with the cup ontop, that is called a protein skimmer. It is pulling garbage out of your water that would cause nitrification if it settled in the tank. It is overflowing, that means that it needs adjusted. There should be a knob somewhere to adjust the flow. Try opening it up more. My skimmer cup gets emptied out once maybe twice a week.
Water changes. Good for you! 10% weekly water changes are what you need to do! It is better to do them weekly, but bi weekly is good.
Why are you dosing calcium, alk
...everything for that matter. You don't have any hard corals that would be using these elements in your tank so the elements that are supplied by the salt you are using would be enough. Also, if you dose anything into your tank you need to test for it.
The things on your rock, those are called aiptasia. They are glass anemone. They are bad news. You need to kill them off. Some use boiled water or lemon juice squirted right into the mouth. I prefer a product called Aiptasia-X. You can also just remove the rock and boil it in water. Do not try to manually remove them! When they break, they release spores that will land around the tank and become new aiptasia. Don't worry, they aren't that bad to deal with.
The algae. The red stuff is actually cyano
bacteria. Remove it by just siphoning it out of the tank. The algae can just be pulled or scrubbed off. Do this before your water change. This stuff is caused by too much phosphates and nitrates in your water. This is coming from the fact that you are overfeeding, so cutting back and physical removal will start to address the issue.
Any other questions, feel free to ask. It isn't too much to be overwhelmed about. You are doing good!