No it's not normal it's 180 days = 6 months. You should check at the time you got stamped and told the officer. That's what l always do. It's your responsibility it's your passport and visa
As todd mentioned you need the new job first it makes life easier. If you leave the current job your employer will cancel your work permit you visa is tried to that work permit so in essence you visa is also cancelled. So you will have to leave and come back on visa exempt. You then find a new job get your paperwork from employer go out apply at thai embassy for non B 90 day go back and your new employer applies locally for the visa extension and work permit
It's your visa that allows you to enter not your course. Once you have the visa you can come and go as you like it's multi entry so enjoy you live in Thailand 5 years now
Yes print it to show when crossing they have it on their system anyway but they will want to see it. They will then stamp your passport make sure you check it is 6 months stamp .