1a. Joe (I tried to find another name fitting, but I couldn't...)
1b. Above 45
1c. Married, wife named Betty, quiet little person spending her free time crotcheting, he calls her "Betty, why the hell......", no children.
1d. A "decent" man working hard to make money for living and he has to suffer all those empty-headed, ungrateful cowboys who always kill/get lost/let coyots eat etc. Aguirre's sheeps...
2a. I see boys whose relationship is getting closer
2b. Aguirre sees all before and after

When they start making love, he stops watching and with a sigh he sits on a stump to wait.
2c. To avoid arriving when they're making love - in a sense that he is just again confused and disappointed by his workers and this confirms his attitude that nowadays all young people are worthless (sigh again). It's his personal burden to manage with such hopeless employees, and nothing can be done with that, he just has to live with it.
2d. "The binoculars was (for me) a hint to Jack that he could see what was going on from far away -- implying that he possibly/probably saw what they were doing..." - I agree with that , so - in a way - he did let him know what he had seen.
2e. No talent

3. I agree with
rimasworld that Aguiree was first of all a tough businessman, who has seen a lot in his life and was bored (blase?) and believed that nothing could surprise him.