Hi we have a Linksys WAG160Nv2 and we are getting slow speeds

(See below)
First of all the router says its not designed for multiple PCs???? We have 2 phone 1 console and 3 pcs nearly always connected the the router, if the router has been on for a few days it will drop out.
If downloading it speed isnt constant as in, it downloads for .5 seconds, stops, then downloads all in the timeframe of a few seconds???? like it cant handle 2 things at once.
We also has 8mbps dsl, we recently switched to this plan, about on the 20th of something, then our speeds rocketed to 6-7Megabits and 600-700kilobytes
But now they only hit 300 if theres only one device connected
Finally is this test what it should be? anything wrong? we also use WDTE exchange.
Thanks in advance