Q: OS x 10.11.5 wifi issues

These two statements contradict each other:

I Picked channel 7 because it was the only one that my neighbors were not using when I did a scan.

The only one is my router on the list.

If your neighbors appeared in a scan, don't they also show up in the list of Networks you see in the Option-Wi-Fi display?

If not, can you post an estimate of how many neighbors there are?

That would be a good choice, but there is a problem. The channels assigned in this band are for 802.11b, which only provides 11 M bit/sec.

By the time you are each of your neighbors moves to 802.11g/n, there are only THREE channels available here. Each nominal channel spills up two channels and down two channels.

so when you pick channel 7, you are already colliding with two other Networks.

Duane has a similar problem with his network, and choses a similar channel. This print of frequencies if from WiFiExplorer, and inexpensive Utility with a three day free trial.

(click to enlarge)

Duane has at least 6 other networks in range. You can see that his choice of Channel 5 impinges on at least four others.

You both would be better served by getting a Router with 5GHz band available, where the effective channels are wider and there is far less competition.

EtreCheck is designed to be easy to install and then remove when you are done with it.

Etrecheck does not even have to be Installed. You can unzip and run it directly from the downloads folder. It does not Install any intrusive system extensions -- it just uses readily available system calls to do its job.

If you get a Router that has the 5GHz band as well, you can either replace your current Router, or ADD the new Router to it. Almost very Router that can do 802.11g/n can cooperate with other Routers to form a "roaming Network" as shown in these diagrams form an Apple article:

The 'Wirelessly Extended" network, by contrast, can be much slower, because half of its bandwidth is spent forwarding from/to the Main Router.

Exactly the same issue - MBP drops wifi, other devices stay connected. I use two different wifi networks: VZN JetPack or Centurylink DSL. Happens with either one after random amt of time. If I turn off wifi and turn it back on, sometimes it fixes it for a while. If I reboot, sometimes it fixes it for a while. But, the problem always returns. My other devices (iPhones, iPad, Win8.x) never drop. Been having this issue since "upgrading" to el capitan.