You would be suprised - with a population of around 70 million, Iran is one of the biggest markets in the Middle East. Having lived in Iran for one year, I can tell you that the shops are full of everything from Western Digital drives to Intel chips. The embargo only causes problems with the very high end of the market.

You can only half do it. QoS means prioritising packets - sending important packets before less important packets. So, you can prioritise VoIP, outbound. You can't do it inbound - only the router at the other end of the link can do that - and since that belongs to your ISP, you can only do it in one direction, unless your ISP offers it (unlikely on a non-business type product). You've also talked about bandwidth reservation - same deal applies. Since a voice call goes in both ways, I think you can get the idea. Good luck!