first off, +t for the first moderately successful taping job. and to have such a nice soundman is a true luxury and i hope that you thanked him many times
I, too, was fortunate to have a friendly sound guy at my usual venue when i first started that always dropped great knowledge on me.
i have heard/read here that the line-in on the jb3s can be a little sketchy. as far as levels, what is your peak value. should be a negative number in dBs. What audio software are you using. Soundforge, Wavlab, and Cool Edit all have very reliable normalizing applications. some folks say that normalizing can cause distortion or add noise to your signal. I use Soundforge 6.0 and have had no problems normalizing to the peak vale and NOT the RMS value. It was discussed in a thread earlier this week about how normalizing using the RMS value will degrade your audio. So if you use Soundforge, normalize using the "Peak" value option.
hope that helps and if you have anymore questions, fire away! we are all here to help each other out in this great hobby
Brian