Thanks for all the excellent advice in this thread. It has already helped me to realise a few things:
1. I don't yet have a system I really trust. I felt my NA list was getting too long and my system was not bulletproof enough to ensure nothing fell through the cracks. Until I find a system I trust to handle my work life, I certainly don't trust it to dump my personal stuff into too, and as long as I hold off from that I'll never get close to the "mind like water" state that would actually help with the decision making and "doing". If others are handling hundreds of projects and thousands of actions then if my system was working maybe I shouldn't feel so overwhelmed.
2. I needed to look again at the tools that I use. I wish I could use a Mac with my work! Then I would have the choice of Omnifocus or Things, which I understand are both pretty good. In the last week I have switched from Jello to ClearContext and it is working well so far. I really like the ActionView and filter options. However, there doesn't seem to be an easy way to sync with Toodledo to my iPhone without losing track of either the context or project, but I'll post about this in the other forum.
3. I probably do have more work to do than is reasonable for one person to manage. There were actually two of us covering Europe before October last year but now it is just me so I have double the accounts. I don't see this changing any time soon but I intend to be more brutal in focusing primarily on the projects that are truly going to get me to my goals and let my boss know what accounts I simply don't have the bandwidth to check in with that often.
4. It is really encouraging to know that others out there are having similar challenges but have come to terms with the long lists and found ways to keep soldiering on. I feel really energized by the support on this thread and the thought that with some more patience and determination I'll get the hang of this eventually.
5. I'm going to try the method of allocating chunks of time to blitz through context lists. I'll also try taking a project focused approach and see how that works for me. I'll report back here how I get on.
Thanks again for all the great feedback and ideas!