Nothing is more frustrating then your machine causing you problems especially when you have invested so much time and money into it. I would suggest walking away for a day (i call it putting it in timeout...lol) then coming back and rethreading both the top thread and reloading the bobbin. Put in a different needle, and I would use a practice piece of backing, top and batting until you get it working again. I would suggest if possible have someone else in the room to watch when your sewing to check things such as how the thread is coming off the cone and feeding in the machine and how it looks when your sewing. Just to make sure everything is going smoothly and nothing looks odd. I noticed you said you has loosen the screw on your bobbin case and if its like mine there are two screws and make sure you are adjesting the correct one. I find many vidoes on youtube very helpful and better then most the company will send with your machine as its real people fixing problems. Also on this practice run I would use a different color of thread for the top and bobbin to aid in troubleshooting if you are having issues. If you are having looping on either side of your fabric you can see which tension you need to adjust. Also if you can try a different type of thread it may be you machine simply does not like a certain brand of thread. Also what type of material are you trying to sew on? As I find fabric with a coating on them or metallic or batiks I have to use a larger needle size and go slower than my normal speed to stop me from having an issue with skipped stitches. Also I find on days when its colder and warmer I have to adjust my tension to match. The main thing is to not get frustrated as this only makes things worse. Do you have anyone close who also has a longarm that could possibly come over to help?