I agree. I do think they are some kind of scale. Your fruit looks a little mottled. Insects can carry viruses that infect plants especially if you do not have a resistant tomato. Tomatoes are heavy feeders. They need about 6 hours of good light a fairly large pot to accommodate the large root system. I use 18 gallon muck buckets that I have drilled holes in. People have gotten away with 5 gallon containers for a small tomato. MG potting soil works but I add about 1/2 cup of tomato food when I plant the tomato and I give it side dressings at first flower, first fruit and monthly thereafter.
Control ants with ant bait, they will bring and protect sucking insects from predators. Besides light, nutrition and growing room, tomatoes need air. If your balcony has a solid wall and it is cement then you have the worst of all words. The solid balcony would block air and the cement would reflect heat and cook roots on a hot day.
If you really want to garden try applying for a plot at one of the city sponsored community gardens. There are nine of them in the city. Most are small 80-150 square feet but are a good size for a beginner. All the gardens have a waiting list so you have to be patient and attend every meeting. You may have to wait months to get a garden and some have 2 year waiting lists. The gardens meet monthly. The best time to get a garden is in July and August since that is when people usually have to give them up if they cannot pay for or take care of them. Each garden has their own set of garden rules in addition to the city rules. So be familiar with the rules of the garden you apply for. Tomatoes don't grow well in all of the gardens especially the ones in the wet areas. The gardens in the drier parts like Makiki and Hawaii Kai may be better for tomatoes.
In Hawaii, we have to have disease resistance. Don't try to grow anything that is not disease tolerant. Grow red current, spoon, sungold (cracks), sunsugar, Kewalo, Celebrity, and red cherry. They do best in a humid climate and they have good disease resistance. Once you succeed you can move on to the more challenging ones like the heirlooms. They usually do not have nematode or very much resistance to viral or fungal diseases so you will have to baby them a lot more. They will need to be on a weekly fungicide program. I have grown Brandywine, Big Beef, Early Girl, Amish paste,spoon, Napa Grape, Kamuela Grape, Golden Rave, and New Big Dwarf successfully in pots off the ground and Brandywine required weekly sprays. The heat tolerant tomatoes were Heatwave II, Sioux, Arkansas traveller. The cherries for the most part are easier to grow than larger tomatoes, they are more productive and they are more heat and disease tolerant. Spoon is a weed in my yard.
With the amount of light your balcony gets, you would be better planting something that can tolerate more shade. You still need to get the plants higher or get a fan on the balcony to provide air movement. I think your environment is not the best for tomatoes. Tomatoes are not the easiest of beginner plants.
Happy gardening in Hawaii. Gardens are where people grow.