With help from Alex Taylor (ATShell author) ATShell is working and close to an acceptable solution. Some minor details remain.
ATSHell invokes InJoy and the Injoy 'autostarting modules' invokes Firefox without a problem. There are some shutdown and unzipping quesitons, but it looks like a workable solution too.
Still waiting for the eCS demo disk to further pursue the bootAble solution. Then I'll pursue the IRQ question, etc.
The modem is on Com1, it is Zoom 56k (external).