single stepping TS68000 microprocessor
tl, dr: you don't need to make any circuit. Use 'trace' mode instead.

The 68000 has the ability to cause an exception on every instruction. This is the Trace bit, set in the Status Register (SR). When Trace is set, the 68000 executes one instruction, then branches to the trace exception handler routine whose address is at vector 9 / offset 0x24, from which it will branch to your debugger.

I also found reference to a complete design that includes the ability to single-step by manipulating DTACK*. Link here: https://github.com/jefftranter/68000/blob/master/TS2/v2/ts2.pdf