About getting the CD to boot:
If you know how to use your first suggestion of using a WinME boot floppy to get access to your CD, then the same is adequate for a FreeDOS floppy or for UBCD.
The problem, according to your screenshot, is that you are selecting too many programs/drivers/tools/STR's to start during the booting process ( "RAMDISK: too big for memory" ) .
The line "SHSURDRV not installed" is the one indicating that your CD is not accessible (you are out of RAM, apparently).
Selecting less drivers to be loaded (you probably don't need USB for example), you might be able to get it work.
Try "playing around" with the several options of memory managers available, for example (defense modes; or selecting each driver on/off with F8 ).
About changing the FSB, you should first resolve the CD problem
. In any case, old hardware is not so tolerant to errors.
IMHO, if you know exactly
the jumpers to close or open (nowadays it is easier with no jumpers
) , and you have experience with those old 486 processors AND mobos and you know how to change the BIOS settings for such old mobos, then it is "doable" (but not so recommended, IMHO ) .
But you might want to take into account that more FSB means more electrical stress and more temperature, both problematic for old hardware.
Making aside your hardware
project, if you want to try old programs or old games, you may want to try a newer system with some virtual environment with low requirements. An example would be to use DOSShell from http://www.loonies.narod.ru
together with DOSBox http://dosbox.sourceforge.net
. There are other options too.