Not sure about the remote documents question but for the redirection if you are on a hosted or on prem version as opposed to Cloud version of Jive you can set up redirection rules in the admin console at System -> Settings -> Redirection Rules. If you are in Cloud the feature still exists but you have to open a case with Jive support to add it for you.
I'm not so interested in redirection as actually finding the links. I believe there are very few (if any) links to the space I want to delete. It would be much simpler if there was a simple technique to query my site for references to the link.
Thanks for raising this question around the space deletion and 20 remote documents. As Eric has mentioned, redirects may be managed directly via the Jive Admin Console or through a support case, if you're a Jive Cloud customer.
As for the 20 remote documents, I believe you're running into JIRA bug JIVE-59596. With this bug, the count is always 20. You may safely ignore this and proceed with the deletion as long as you're certain no SharePoint integration exists.
Let me know if you have any other questions with this.