Sounds like you found some nice trees. One problem is that you probably don't know what varieties you have, but it should not prevent you from enjoying the fruit.
Not sure where you are located, but probably your trees are dropping their leaves and going into dormancy.
Fruit trees are not all that different from other types of deciduous trees, in this respect. I would give them a good watering before the ground freezes. The idea is to keep the trees evenly watered. This may require watering more often in the hot weather. Layers of mulch at the tree bases will hold down the evaporation to some extent. You can check the trees periodically by carefully digging down near their bases to check if the ground is dry, or not.
You want to water heavily, but not too frequently. This encourages good root development. You can put an earthen ring around the tree to hold in the water during irrigation so that the water does not run off before it can be absorbed by the trees.
Once the ground freezes, no need to water.
Answered above.
I like to use a slow release fertilizer, like composted cow manure. I give the bases of the trees a coating just before winter, so they are ready to jump off the next spring. I also cover the area (inside the drip line) with composted mulch. You can rake these two materials into the top few inches inside the drip line. Be careful not to damage any roots, as some fruit trees (like dwarfs) tend to have a shallow root system.
The thing you didn't mention was pest control. That's more complicated. Start thinking of giving them a spray of dormant oil just before spring. If the fruit you picked was not attacked by insects, you don't need an agressive spray schedule. Pruning is also complex, but you should do that while the trees are dormant, or you will just encourage more growth. Cut out ingrowing and crossing branches, for starters.
Hope this helps,
Sherwin