Your readings are telling us what your Wifi connection is not your broadband speed connection speed.
You have told us at 74mbs is the speed between you and your router, that's why when the connection drops your connection to your router and your device is still connected and still the same speed.
If you want me to remote connect to your computer and look at your settings drop me a pm, it only takes 5 mins to set up a remote connection.
If you want to know what speed your broad band is doing that's from the connection on the wall to the big internet world try this broad band speed tester .http://www.broadbandspeedchecker.co.uk/
Click on Begin Speed Test.
Its normal for it to say its downloading as that is what the test is all about.
You will then get the correct results.
* Interference with Wifi Signals (Near the aerials)
* Digital Phone Reciever (move it seen this lots of times).
* Microwave oven when on.
There on the same radio waves as your wifi connection and thats why a Wifi can drop out but not your router to the outside world.