Hi...if you haven't already done so, go and join the Yahoo group for JanomeHorizon 7700. I think there is a manual available there, or one of the members can email one to you.
Sorry, can't help much with your other questions regarding the thread. Oh...I think I remember someone on the yahoo group mentioning putting the cone in a cup behind your machine and they taped a paper clip to the top of the machine for the thread to run up through and then through the normal threading guides. Perhaps that would work.
Blessings
Janice