Removing the seeds will not necessarily make the pepper less hot.
The heat of a jalapeno comes from its capsaicin, a membrane in the peppers' pith or ribs. However, when the seeds come in contact with the pith they may become coated in capsaicin which can make them spicy.

To make the pepper less spicy, you will want to remove the seeds and the pith.
Remove the stem, then cut the pepper in half lengthwise. Use a spoon and scrape out the seeds and membrane. The pepper can still be spicy, but a good portion of the heat is stored in those parts.
During this process, avoid touching your eyes to prevent any irritation.

Yes, with the right conditions jalapenos can produce more after the first harvest.
After the first fruits develop, jalapeno plants can keep producing for another 30-40 days. They may even continue producing as temperatures start to drop towards the first frost. Jalapenos prefer warm weather, so as the temperature decreases, so will the quality of the plant and fruit.

Jalapeno seeds can be harvested from the pepper and saved for another planting season. Remove the stem from a ripe pepper. Then, cut it in half lengthwise. Use a knife to scrape the seeds out of the pith. Spread out the seeds in a well ventilated area and allow them to dry for several days. Store your pepper seeds in a cool dark place to plant another season.