In answer to your questiona
1. We recommend that you put a copper pad on all layers for vias.
2. If you place a via on a pad then this via will be filled with solder during the finishing process. I am not sure what you mean by "wicking" but I imagine you will need to make some allowance.
3. Please have a look at the downloads section on our services page. You may find something to help you here. We dont have any official recomendations for this.