Is there a way to make it re-scan the whole sharechain and display all my shares?
Are you using the default interface? The one I like is
https://github.com/johndoe75/p2pool-node-statuswhich you can see in live use here:
http://us-east.royalminingco.com:9332/static/If you want the "time to share" info down on the miner line, you need to go into p2pool-node-status after you clone it and try "git branch devel". That will update it to support the extended API stats needed.