I believe the layout of the current MonoGame is is a bit different, not personally looked at that branch as it's only being maintained by the MonoGameTeam at the moment.
Hoping to include it more in V2
Will have a look when i get a chance to replicate the above issue, the duplicate Ads may be a result of late loading with the pubcenter control and possibly having multiple Game components added (but from memory, pubcenter it'self controls this.
As for the stretching I've not seen any reason why a local house ad would stretch unless your image is already full screen?, or you are not checking / changing the AdWidth / AdHeght and position correctly when the orientation event is fired (I
left the orientation code in this time with the example in source)