MicrostockGroup

You write an email to support asking them to terminate your exclusivity. After 30 days you are free to upload/sell anywhere else. At the moment of terminating your exclusivity all your images will also become non-exclusive, except for the assignment images. If your images have been online less than 6 months you can delete only 30% percent of the total.

The other agencies have their own methods for uploading and be prepared to have some of your 900 or so rejected. It will be easier if you have keywords, etc. embedded into the IPTC data of each image. I'd research how your images stack up on other sites before uploading. You've mentioned before that your wife uploads to other agencies so you must have some "in-house" information, so to speak.