I think your pest issues and other factors mentioned derailed this plant. No worries, i'm sure you will learn something that will help avoid it in future. There's not much you can do about this grow, unfortunately. It's starting to flower, so at least it'll end at some point, lol... 6-8 weeks more... up to you if the effort is with 10-20grams. the learning aspect may make it worthwhile.
"they" say to not pot-up an autoflower. I'd suggest starting in appropriately sized pots for stage of life. Probably need to tweak the balance of your fertilizer too, but that may be the restult of less than optimal watering practices over time due to huge pot, tiny plant related issues. As long as we don't use our retard strength on the rootball, potting up is a very low-stress procedure that should never shock your plant. We are gently placing a plant in a larager pot and gently covering it with substrate. If this shocks a plant it's some shitty ass genetics anyway, lol. I've done hundreds of 'transplants' and never had a problem nor shocked a plant from it.
Proper watering procedure-
1) water entire pot - no dry pockets, minimal runoff in soil ensures it... 10% runoff minimum for soilless substrates. the amount of water required is what is necessary and not some predetermined volume you choose. The water capacity of the substrate will determine this, not us.
2) wait for appropriate dryback and repeat.
how often you add fertilizer depends. soilless - everytime. Soil has options. Choice of frequency impacts concentration given. In general more often at lower concentrations result in better growth, but at that point you might as well go soilless, if you are adding it everytime.
Early on i'd let the top layer dry (coco) or 1" deep (soils / sphagnum peat moss high water capacity substrates) before repeating and feel the weight of it at its drypoint. If you water at same loss of weight, it requires the same volume of water each time, less some imperceviable weight added by growth in that time. Early on stick to a good wet-dry cycle... later on in flower with a robust root mass you can dabble with more frequent irrigation/fertigation but you still need at least a 33% dryback to avoid root rot. Doing so early will result in less root growth if water is 'too available.'
look up DLI for your region. Maps will show per month the expected DLI i can get per day... this can help you choose how much shade to give it. 35-40dli is gonna be up near max of what a plant can use per day. plants do develop resistance to excess light outside over time, but may need to be slowly exposed to do it. If your area and time of year is only 30 DLI, shouldn't have to shade it, for example.