Hi,
well your original question had 2 parts and the answer has also 2 parts. :-)
1. so first - the &lang= "problem" has already been answered, it has currently no big influence to functionality of anything and you can use JoomSEF and JoomFish together without any problems. The only think we can do here is to publish the patch for JoomFish to make it translate also the mentioned links - I hope we can do this.
2. the second problem regards the Itemid -- here you have to choose from several configuration options that JoomSEF offers - this mean exclude the ItemID yes/no and reappend it yes/no. If exclude it and not reappend, then you have to live with limited functionality, but you will have unique URLs. If you do not exclude, everything will work fine, but you may be facing some duplicated links -- in most cases, those can be also prevented by carefully creating the links. Lastly, you may use some semi-solution by excluding it and reappending. Then the functionality will be preserved and your URLs should still be considered friendly. The dynamic, appended &Itemid part should be ignored by the search engine robots.
Hopefully, this answer is understandable.
Best regards,
ARTIO Support Team