Your bobbins are made with holes on one side for a reason. The reason is so that you can easily tell which way to put
the bobbin in the case and always repeat it. Always wind them with the holes facing then same way (right or left). then place them in the bobbin case the same way (holes facing out or in). Which way to put them in the bobbin case I can't tell you without seeing the bobbin case. Some machine require the bobbin to unwind clockwise or counter. Look at the bobbin case and put the bobbin it so that the thread comes off the bobbin then reverses direction as it enters the slot. In other words the thread must make a 'V' as between exiting the bobbin and entering the slot.
There is no alternative for the DBX1 needle. It is one of the most common and cheapest industrial needles available. In fact it frequently is an alternative for other needles.
Is the eye of the needle that is not working well large enough for the thread? Has the scarf always been facing to the right and it is threaded left to right. An idea is to try a top stitch (large eye) household needle in a size 12 or 14. The DBX1 and the 15X1 are the same except that the 15X1 has a flat on it's shank. It will substitute for the 15X1, but not the other way around.
I hope that this info helps in some way and isn't too confusing.
I do not have much experience in free motion sewing.