Better boys should set fruit fine in the 80s. The flowers drop off normally after the fruit sets. They grow those in Texas so you should not have a heat problem.
There always needs to be moisture but just not wet. It really depends on the soil and how well it drains. If the soil is still moist when you go to water it then there is no need. If is dry and inch or two down its also no problem. I also don't know if you are on the dry side of the island or not. Many in ground tomatoes with typical top soil will do well with a once a week soaking but not during dry conditions in the 90s or in containers. If you notice the plants are looking stressed or you are getting blossom end rot on the fruit then you need more water. Also avoid the leaves. The native plants in Peru are watered by mountain run off and less so from rain.

what I meant was, the whole blossom falls off, with the tiny tomato. the stem just turns yellow at the breakage point, then a tiny tap or wind will cause the whole blossom to fall off...
many of the fruit bunches have only 2 or 3 tomatoes growing, as the other flowers fell off.

many of the blossoms are also dropping, and then when I open them up, i see tiny tomatoes... is this normal? [...] what I meant was, the whole blossom falls off, with the tiny tomato. the stem just turns yellow at the breakage point, then a tiny tap or wind will cause the whole blossom to fall off

What you're looking at (if very small) might just be the ovary, and does not necessarily indicate pollination occurred.

Watering: as solanaceae alludes to, there are no hard and fast rules about how often to water, in terms of someone being able to tell you to water x number of times a week, etc. Water moderately (not too much, not too little) and do it deeply. Check the soil, if it's not dry at least a couple of inches down or more, don't water.

Also, mulch thickly. This helps immensely on cutting down on watering and keeping the roots cool.

One problem you might run into with "easing off" is by previously watering everyday, the root development may not be that good. Roots follow and grow towards water and nutrients, and if the soil is constantly moist, there isn't as much incentive for them to grow deep.

So, take it easy at first with easing/tapering off, and watch your plants carefully.

I water very little after my plants first go in to "train" the roots. Planting areas and root balls are deeply soaked, and mulch is thickly applied. It's not unusual for me *not* to have to water for up to ten days or more after I plant, even in the absence of rain. I find that by doing this, I get healthier plants that are better able to take the stresses of a warm/hot summer climate.

With temps in the 80's, I figure you should be able to get by with watering no more than once every 4-5 days, maybe even less frequently than that -- in those sort of temps, I generally water every 6-7 days or so. But that is just a general guideline/suggestion (and I don't know your soil composition or how well it drains). Of course, watch your plants and check the soil moisture to determine how often to water. Temps in the 90's (especially mid/high 90's) are a whole different ballgame, as solanaceae also indicated. More frequent waterings might be needed, if you encounter higher temps.