wifi issues

Troubleshooting wifi can get kind of complex, there are a lot of different things that will affect it. Start out by going through this article, some of the steps might help:

http://support.apple.com/kb/ht4199?viewlocale=nl_nl

Also if you can plug your Mini (or some other computer) into an Ethernet port on the router & check the speed, that will help. If you're getting slow performance on wifi but not on Ethernet, then it's a wifi issue. If it's slow wireless and wired both, then it's something else (e.g. the modem or ISP or router settings)

 

How are you measuring 30Mbps from your computer to the router? Or are you mistaking your internet connection to your router here?

As far as re-installing ML, you can by using the CMD+R key combo you just need to hit it at the right time. I run into this a lot myself. You should hit it just after the screen goes from black to gray (before the iMac chimes).

 

someone might have set up a wireless internet connection near you with the same channel as you. I would specify a different channel and then run speedtest.net and keep changing channels trying each time until you get the best connection.

 

This is how I solved the issues in my old apartment. There were so many routers in the area. Most of them were on channel 6 so I changed to 3 and I got my speed back. It also helped with drop outs.