How is my internet speed?

It's a fairly fast connection.

The reason it's as fast on wifi as it is directly connected to the modem, is that wifi has much more bandwidth that your internet connection. It could be up to 450mbps (or more with the latest 802.12ac modes). (Real-world rates would be ~50% of that.) Compare that to your 22mbps Internet connection, and you can see there is a lot of headroom left before it would saturate the wifi connection.

You can see that your browsing speed is not limited by your wireless connection, but might be some limitation in your router or modem.
Your wireless can send and receive much faster than your internet connection. If you go to a wireless router that can use the faster ac connection - that assumes that your MBPro also has that ac card.
And, you still won't get a faster internet than your internet connection provides. That ultimately will determine the speeds that you see through an internet speed test.
You CAN use faster wireless for sharing files with another wireless computer. You would then get transfer speeds depending on the wireless cards in your computers, not limited by your internet connection.

1. You are already not getting (complete) full use from what you are using now.
Will there be some additional benefit from an ac router (assuming that all your computers have ac wireless cards)?
Yes. You can expect improved reliability of your wireless network, because of enhancements to the wireless protocols, which you would then be able to take advantage of. One of those would likely be an apparent (maybe real) improvement in your internet performance.
If you are currently deciding if you want to upgrade your wireless connection, then why not proceed with that?

2. Yes, you should expect faster communication within your own network.

All that may then push you to upgrade your internet connection, too, which may mean upgrading your modem…. Is your technology treating you OK now?