Mady,
you're right, at the moment we don't support dropdown lists. This could be added, but I'm interested how you would like to use them - do you want to specify a static list of string values or do you want them to be looked up elsewhere (dynamic)? The first option I could see making a release sometime soon, but the second is a lot more complicated and I even doubt whether it's worth providing since configuration in your custom node could easily become rather complex.
As far as the tabs go, no, everything ends up in the main tab. We don't plan to enable splitting of these tabs. Would you like to put all of the fields in your own tab or would you like to divide different fields for the same node into separate tabs?