There are a few ways you can get faster WiFi connections. The easiest way is to just get an Airport Extreme router which you connect via Ethernet to your iMac, then let it make the WiFi connection to your AP in the other room. This is what I would do.
The next option is to upgrade the WiFi board in your system, but it's not easy and you won't get MIMO so it won't be the max of Phase1 or even Phase2 802.11ac which many routers now offer. Here is one source for the needed kit to replace both the WiFi & Bluetooth boards you currently have in your system to a combo card: Apple WiFi + Bluetooth 4.0 card to MiniPCIe Adapter for 2009, 2010 & 2011 iMac's.
Both of these solutions don't address the USB port part of your question.
To improve this you'll need to use a Thunderbolt dock which then offers USB 3.0 services. There is no means to alter the internal systems USB ports.
If you decide to do go with a TB dock then you could connect via the faster USB connection a USB WiFi unit which could get you an 802.11ac connection.