I just had something similiar happern to me but the bottom thread was not quite that bad. After changing thread, needles, rethreading many times I took it in to a great repair shop. (in a panic of course). the problem- the upper tension knop was completely loose and there was no upper tension so thread was way to loose on the bottom. the repair lady said this will happen due to putting the presser foot up and down many many times. I had never hear of this but after tking the knob off and tightening the upper tension screw the machine works great. The lady was really nice- only charged me $32 and worked on machine for 1 hour while I waited. she also showed me some other tricks on my machine. My machine is a Brothers 1500s.
Perhaps you DH could check this out for you or maybe yourself if.