Under this scenario, can I combine "special pass" and leave days?

It depends. If you plan on leaving your local area than no. I don't know the reg on the top of my head TBH. You have to begin leave and end it in the local area. So I suppose you could take the two days off then if you plan to travel than you have to leave on the starting day of your leave. The reason for this is line of duty determinations if something were to happen like a car accident and were out of the local area you may end up paying the bill for any treatment. Also there is being present for duty issues as well. A pass can pulled at the convenience of the commander. A signed leave form requires a more justification to be pulled.

Can't tell you the reg for AF, but the personnel regs for leave is, I believe, the same across the board. A pass can generally precede leave, but you would have to physically check in at your unit, or in the area between the two, otherwise, it's all leave.

You'd need to provide more detail, and the answer may be AF specific. And, the answer may involve your intentions. If you're looking to combine all of those days to travel for the entire period, that may be problematic. If you're using the pass and leave days to remain in the area, then that may be workable (although many commanders still may not authorize it). If I had a soldier wanting to travel outside of the area, and wanted to combine all of those days, I couldn't authorize that. If they wanted to take Thursday and Friday off using the special days, and then sign out on leave first thing Monday morning (and then travel until Friday), I'd be okay with that as long as it didn't conflict with any missions.

http://static.e-publishing.af.mil/production/1/af_a1/publication/afi36-3003/afi36-3003.pdf Here's the military leave AFI.

I am not sure but when you are on leave, there has to be a work day (where you return) in order to take more leave. The passes; you may have to work that out with your supervisor or super.