1. Psammacora is one of the easiest coral to take care off. It is also very invasive and will encrust and spread everywhere, even the branching kind. They don't require amino to thrive although it can help accelerate growth.
2. You can just spread out the dosage so instead 1 drop every 2 days, do 1 drop every 4 days.
3. Dosing amino is only necessary when you have lots of corals that are consuming aminos faster than you can replenish them with water changes. It sounds like you have a newer tank and dosing aminos is often a cause for algae out break in newer tanks.
4. You have a skimmer for a 10g tank?? Are you running into nutrient issues that you need a skimmer? Usually skimmer not needed for nano tanks and it's just a way for vendors to sell you equipments you don't need. Water change is your friend for nano tanks.