PC-Task is the program you need.... version 4.4 being the latest and greatest, which is still 10 years old or so! More RAM will help you a lot if you can get it, as will an accelerator, but a 68020 should be enough to get close to XT speeds. You can run MS-DOS up to 6.22, but you're probably best with 5.0 as this came on DD disks rather than HD ones which your 1200 can't read.
Alternatively, get an A500! You can get KCS PowerPC boards for them fairly easily which have an NEC V30 on them (10MHz), 1.5MB RAM for the PC and Amiga side, and will access all the ports of the Amiga, as well as providing up to VGA resolutions (VGA is only mono of course!). A big box Amiga is still the best method though, of course - the GoldenGate being the best bridgeboard out there as it goes up to 486SLC2@50MHz and uses SIMMs instead of ZIP RAM. You may of course have to sell an arm/leg/granny to get one...