Looking at the logs it seems that it is your JDBC driver that depends on JDK 6: the NoClassDefFoundError exception is thrown while BTM looks for a setter in all the class' methods so one of them must take a java.sql.Wrapper as an argument or declares it as return value. This happens in logic internal to the VM so there is very little I can do about this.
I've found these two versions of the AS400JDBCXADataSource online:
None of them reference a java.sql.Wrapper object so I wonder if you are using a different version ?
Also, have you simply tried running your app with JDK 6 at least to see what happens ?
Finally a bit unrelated note: you defined URL, username and password driver properties. Those are specific to Oracle (there is no URL property in AS400JDBCXADataSource) and you have to use different ones with AS400JDBCXADataSource. My guess is that you'll need at least user, password and serverName.