When determining if a battery is good for a particular application you need to know how many amps the application requires as well as how many amps output the battery is capable of...
I have found nowhere that states what amps the Panasonic is capable of delivering... that makes giving a recommendation harder when we are talking about VV or VW applications on a PV. So I won't recommend it personally even though I suspect it will work, we just aren't given specific numbers to base a recommendation on. BTW, the eFests are as good as any IMR battery and just because you aren't impressed with how long they last, doesn't make them bad... That is a typical amount of time on an IMR whether you like it or not, it is what it is.
To calculate amps... you use the numbers you gave for watts and ohms and then use an Ohm's Law calculator. The range you gave can't be used by themselves... you need to know which were being used at a particular time. An example of why would be if I used your max numbers of 5v and 2ohms... it would give us 12.5w and 2.5a. Since you said you didn't go over about 9w, obviously those where you.
So now you know, you must use exact numbers to be able to find out the amps you are using... PS. If you don't have an Ohm's Law calculator, there are a "million" of them on the web, just search for them and pick your favorite one.