When do I start feeding?

You generally want to wait until the plant has at least 1-2 sets of true leaves or nodes before you even consider a light feeding. Usually this will take at least 2 weeks from germination. Ultimately when you feed depends on the soil you're using - if the soil is high in nutrients then it can go longer than 2 weeks. E.g. If using Biobizz "light mix" - you will want to start the nutrient schedule after week 2. If using Biobizz "all-mix" - you can wait more than a month, and even then nutrient feeds are lower throughout the grow cycle. Good luck!

I agree with Creepy_Steve. Which soil are you using? Also, I would only water immediately (8 cm or so) around the seedling at first. Unrooted soil stays wet for too long and will attract gnats.

btw, that was just some random link i found witha quick google search.. the parts i mentioned were fine but i did not read entire thing, lol..

your soil will have nutrients aplenty for the tiny plant for a while. Observe and react... soil is a wildcard dependent on what you bought, what you added, etc.. even the same products could vary from batch to batch but not too much from the 'better' sources, whatever they may be. Watch for any hint of paling starting at the bottom and start ramping up your fertilization. N is likely to be the first sign of deficiency... take not of when it started. Next run you can start to supplement with fertilizer in a preemptive manner with some confidence. Some soils can keep a plant sustained for a couple months, others may only last a couple weeks. too many variables to give specifics.. just understand the gist of it... https://gardeningmentor.com/how-to-water-potted-plants/ -- though i'd say 1" deep vs 1-2" deep... weight of pot... top watering sections... this plant is no different than any other in this regard.. stick to a proper irrigation cycle and it'll go well. if the plant is tiny relative to pot, a column around it is ifine, but make sure the water goes all the way down to bottom (the 'deep watering' mentioned in the link above.