For ServerA/Acme1 you should be able to just use the Domino server name. Check your personal address book for connection doc. Also if at one point ServerA/Acme1 had another IP address the Lotus Notes client will have the old IP in cache.
As for accessing ServerB/Acme1 and getting the cross-certification error. You did not mention at what level did you cross-cert. If you only cross-cert the two server with each other you will get the cross-cert because your ID is accessing the other domain.
Exchange 2007/BES 5.0.2 MR2