Q1 / Q2. I agree with Steve on these.
Q3.
With OpenUI you start with one of the base Agentry control types and extend from there. This gives you the link between Agentry and your control so you can access Agentry data and also call Agentry actions.
Your OpenUI control will exist on a screen in Agentry so within that context you have full control. For example, we have created integration between Agentry and ESRI to display an interactive map. This map can be rendered as a full screen in Agentry or as a partial screen depending on the requirements.
Either way you will want to start with one of the adapter types depending on the type of data you want to pass into the control.
--Bill