For issue #1, can you give me any additional information such as error logs from Apache (/var/log/apache2/error.log) or your javascript errors? Need something to debug with please.
For issue #2, I used to have the slide 0-30 however people requested a lot higher (300). I went in the middle and set the scale for 0-100. If the slider is hard to use you may tap the input box and manually enter a number that way.
For issue #3, to rule out a problem with my web app try to navigate to the interval program and check the preview there. You would use port 8080 instead of 80 to access the interval program instead of my web app, thanks.
Update: After our discussion on the other post I assume your issue #3 is due to the interval time being 0 minutes. Set this to something very high to run it only once (1439).