Sorry but I don't know what kind of mic is good to 30 feet. I have gotten the ION wet and there isn't an issue.
The built in mic is underneath the ION on the blu part of the case near the PodZ. There are two odd shaped holes.
I'm concerned that you has to do all that to install the WiFi Podz to get it to fit. I was able to install without issues. It was tight but it fit without modification.
The mic jack is internal (under the Podz cap). Take off the PodZ and reinstert your microphone or another one to see if the volume increases. What microphone do you have? Is there a volume control for that? Is there a level that either cuts off the microphone or reduces the recording level?
Two things :
1) Have you tried to record without the external microphone? How is the level there?
2) I'm still not clean if you have copied the files to your computer and then loaded one or more into the Power Director program to see what the volume would be there?
By cutting off the locating pins and drilling the holes, you have probably voided any warranty you have.
Use the information from above to work with your videos. With your modifications, I cannot try to duplicate what you are seeing.
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BoilerPlate: To posters who ask for help -- it is nice to thank the volunteers who try to answer your questions !
Anything I post unless stated with a reference is my personal opinion.