Query: Is there something I can investigate to fix the following series of events?

New Smaller world, fortress mode year 5, Slow start a bit of lag, expected on a 12x12 map. On the 11 of Slate the thing freezes until windows closes the program.

I go back in to the embark autosave. Again it freezes on the 11 of Slate but I force it to wait and the game does resume, only to freeze again on the 18th. I force it to wait again and it freeses on the 21st.

I no longer consider this playable but I really don't want to abandon the map, it is really great with a named mountain peak, a stream, and a woodland. Please advise.