This page may contain information that you've already referenced or knew beforehand, but I figured it might be useful due to the fact it has a sample CTSYN.INI file included. This INI file contains a SBPort setting that the error message you gave mentioned; it might be the key to getting the DOS driver to load.

Also, I would recommend loading SMARTDRV.EXE; place this after the SBEINIT command in your AUTOEXEC.BAT. This should give you a noticeable boost in hard drive access performance while using DOS programs. I believe you can LOADHIGH this, but with all the other stuff running, high memory may be a bit crowded.