Citrus trees do go dormant. Some of the growth may be in the roots. The tree is small and for myself, I would have chosen a smaller pot. Citrus needs good drainage but likes to have a lot of air space around the roots, you need to be careful not to overwater that can cause yellowing. Citrus trees should be fed while they are in active growth from the time they begin sprouting new leaves in spring until they go dormant in the fall. I use citrus food, but you want a food that is relatively high in nitrogen and contains micronutrients. Your tree will not produce fruit for 5-7 years from seed so I wouldn't worry much now about giving it too much nitrogen.
I don't do seedlings, but cuttings would go into a 4 inch pot first. It would next graduate to a 1 gallon pot and I would use a mix that has more drainage and a slightly acidic soil or use an acidic fertilizer like for citrus, roses, or rhodedendrons. Either more perlite or cinders in a standard potting mix. Citrus trees like infrequent deep watering and hate soggy roots. They also need maximum light and air circulation so your plant should be hardened off to go outside when the weather permits.
My citrus trees are in full sun and I plant my large trees in pure cinder because I don't repot. They need to have regular fertilizer since the cinders provide no nutrients but they can handle everyday watering. My younger citrus trees go from 1 gallon to 2 gallon, then to a five gallon. When they are about 3 ft tall then they can go into their final 20 inch pot. I grow mostly grafted or trees from cuttings so I get fruit within a couple of years even on a small tree.
Happy gardening in Hawaii. Gardens are where people grow.