Alongamento das plântulas por falta de luz.

for that u can use 24h schedule without ik,red leds +Nitrogen (be careful not overdid it)

For seedlings it will be too much. Download simple lux app , 30k lux is your target during veg, during first 10 days of life : 15k max. In few first weeks of flower - 40-50 k, from 4th week bombard max with same distance. Plant grow rate and inner space volume should tell you way more than any advice here ...

The best way to play with light is to measure "ppfd". The simpliest way for that is to get an app on your phone called "Photone". Every growth stage requires different settings, including ration between humidity and temperature - ppfd + vpd = optimal environment

It's not just about the performance. Distance and spectrum are very important. Add a lamp that has 10000k (very white). Aquarium lamps work great for that. After a week, normal growth should be achieved at the latest.

Depends on the light. Depends on what is already provided, if i understand this to be a 2nd light Resulting elongation is one way you can fine-tune how much light you provide. IF it is stretcghin either turn up power or get it closer... getting it closer reduces area of coverage. If it still properly covers the canopy, closer is fine.