look for dos-emu/dosx - but it runs under UNIX/Linux... In the conf-file You can set exact the CPU, the speed, the amount of memory dosemu CPU should use...
But - the behaviour of the emulated CPU executing "unknown" instructions is of course different to that of a - lets say for example - "real" 80186...
The differences between 8086 and 80286 drives me crazy years ago...

latest version of dosemu on sourceforge.net

A further trick to run it unter w2k ist to install mingw or cygwin and then reconmpile dosemu.

good luck....!

PS.: there were plug-in ISA-cards with a complete 8086PC or 80286AT CPU on it to simulate network (Plustek had one), so maybe You may found one, if so, send me a msg, I have some Software for it...