With each Alsa revision I typically see many improvements, these can cause some challenges. While it appears most systems are supported with ease, with an increasingly greater range of Audio hardware there often requires a few extra configuration steps regardless of whether the hardware worked OOB on previous Alsa releases. It's unfortunately the nature of the beast.
Additionally, it appears that some basic troubleshooting steps or methodology have been missed in your efforts.
An experienced TC user would know that to boot a USB installed TC on a Mac you would need to install an EFI compatible Boot Manager such as grub2-efi from grub2-efi.tcz. However by default a CD will boot (blame Apple for that).
reading the posts here I'm not at all sure if you're aware that TC needs to be instructed to use a specific tce directory, when there are various older installations (additional USB's, HDD's and even a bootable CD left accidentally in a CD/DVD tray) to choose from. Otherwise there is no guarantee the desired tce or cde directory is actually being used. This can and has been the cause of considerable confusion for many (usually new users). It's best therefore when creating a USB bootable TC to clearly identify within the boot config file which USB and TCE directory to use using Labels, UUID codes, etc etc..
Honestly if you remove the possibility of tce directory install confusion, I believe at worse case an Alsa config file is all that is required to bias Alsa to use specific hardware. Actually this is how I accomplish this task for obscure or new audio hardware. Alternatively use pavucontrol with pulseaudio to switch the audio source and output.
1. make absolutely sure there is only one installation of TC installed (be that a CD, a USB or HDD)
2. load only alsa.tcz
3. run alsamixer to
a. select correct hardware and
b. unmute require controls
4. if still having issues begin the typical alsa troubleshooting