I can totally relate to what you were describing about the repot. Big plants are awkward!! Yes, I would repot a struggling plant in attempt to improve its' health too. (If this is done regularly, it's not as traumatic, for future reference.) I think you would have noticed if the roots were mushy, so that's good. From this additional info, I think your plant is having a hard time adjusting to the new conditions and disturbance. It sounds like... there was very little soil before, from the roots having filled the pot. If so, the roots around the outside of the root ball were adjusted to being dry most of the time. When this happens, the soil inside the root ball can get so hard and dry that it can't get wet anymore. It's possible your plant was getting so dry that it was suffering from lack of water, from being unable to have moisture available - just running right across roots, but not being able to soak into what little soil there was. Like a very dry sponge that doesn't get fully wet if you just pour water across the top. If still on the track of what was going on, now that the roots are surrounded with moist soil, there may be some rotting. Letting the soil dry will help combat that. If you packed the soil tightly around the roots, loosening that by gently pulling the plant up a bit, and/or fluffing around it with a fork, can help increase the amount of air in the soil. This would also help the portion of new soil without roots to dry more quickly, so you don't end up with a very dry ball of roots surrounded by soil that's always moist, can also cause rotting. Roots need oxygen & moisture at the same time to function. Just moisture = rotting. Just air = drying/shriveling. Hopefully the roots will take off into the new soil. Sending good vibes! It's also possible to use potting mixes that naturally have more air throughout them because they are made of larger particles (and don't contain much stuff like peat that takes a long time to dry out.) If you have an ongoing problem with rotting roots of plants, that would be something to investigate. Sounds like things were going well. Regardless of its' potential to help people overwater their plants, millions of plants are growing well in MG potting soil as we speak, so that can't automatically be blamed every time a plant gets ill. In the case of this particular plant, it may have been better to repot sooner, regardless of soil type, before the health declined. Not a chide, saying for future reference, and as possible explanation of why your plant declined at all. If that's a spot where this plant lived happily before, that's probably not part of the problem. IDK anything about insecticidal soap, so I'm not ignoring that question, just don't have any info to share.

Tall skinny bright orange flower sounds like Vreisea

Likely if you eat tomatoes from the store they are production tomatoes. 1. They won't have the taste like a good gardener hybrid or heirloom tomato (in other word they tastes like cardboard). 2. They are hybrid, when you replant a seed from a hybrid plant, it won't be exactly like the original plant, it will have different characteristic and may not taste as good or have desired traits. I would rather order some seeds online and grow some dwarf tomato instead. If you intend to grow indoor you will need some good lighting and space. Something like this is minimum I would recommend for full size tomato indoor: https://www.1000bulbs.com/product/8256/FC105-S50OD.htm. So as you can see, tomato need lots of light which isn't not going to work in a single room dorm. Not only that, they need lots of soil, at least a 5 gallon container. So it's better off growing something like lettuce or basil indoor, or look for a dwarf or microdwarf tomato variety. Some variety to consider are: Red Robin, Tiny Tim, Silvery Fire Tree. For indoor potting soil, make sure you ask question and find the right potting soil that does not smell and perhaps pasteurized for indoor use, otherwise it will be an unpleasant experience. I don't buy potting soil, but I know "FoxFarm's Potting Soil" have good reputation so you may want to check them out, but I don't know how it'll smell. In my bedrooom I have an "AeroGarden Extra LED" that let me grow vegetable hydroponically, and it's LED light is bright enough to provide light for some extra plants in smaller container next to it. It is full spectrum and would be adequate for small dwarf tomatoes. It have a timer and shuts off after 12-16 hours. It is also very easy to make your own affordable indoor hydroponic setup. However, considering you live in a dorm, I don't know if you may have issues with campus authority who will be concerned with cannabis growing which is quite popular with hydroponic growing (not that I'm trying to give an idea).

Note that spraying twice a day with water opens you up for fungal disease. That might be a good tactic in a desert environment, but I wouldn't do it in Queens. A wash-down at first is great, then I would spray something like neem or permethrin. Then repeat that every few days for a while. If your plants survive the next couple of weeks, the problem should subside as the weather gets less conducive to the mites.