Was the splitter needed? I mean, if I read your original post right you didn't have mic at all and now it seems to work everywhere except in AH.
If so, check the AH Clipboard>Options>Preferences>Game Sounds and see what it says for Microphone. For me it says "Microphone (Realtek High Definition Audio)", similarly to the Speakers and Headset boxes. There may be other options such as "Realtek High Definition Audio [Optical]" or like on my current rig "[Loopback]". And of course the brand may vary. But if it says something related to your video card you definitely don't want that!
If you can find your microphone settings there, the next step is to make it loud enough. Clipboard>Options>Preferences>Voice is the path, there you may want to set Mic Volume to full, uncheck the Auto Mic DB Boost and set the Mic DB Boost slider somewhere between 1/4 and 1/2 to start with. If it's still low, check the Windows recording settings and raise the boost percentage.