When you do load balancing with speedtest.net you'll end up with weird results because it recently changed to use multiple TCP sessions, but only one TCP connection at a time. With the type of load balancing setup you have, parts of the test will use each WAN, so it's normal to end up with results that either match only one or the other, or in some instances, that match neither (as part of the download test can use one WAN and part of it the other). Sounds like you're also expecting a single TCP connection to use the sum of your bandwidth, which is impossible as it must be tied to only one WAN.