If you can grind at all well, you can make a wood tap from a section of your acme threaded rod probably cheaper than you can buy the tap, but it depends how you value your time.
How durable the threads are depends on the species of wood, the engagement length, how stable things are (if the wood shrinks and swells a lot with a steel screw in it, the wood threads get damaged to an extent that varies with how much the wood shrinks/swells - there's also a contrary relationship where more engagement length makes the threads stronger, but also more prone to damage from wood movement) and potentially any surface or penetrating treatment you might give the wooden threads.
For a wooden/steel setup like this, the steel will always win when stressed. "C-clamps" (or G-cramps) are not a typical form/shape for a clamp made of wood, and your testing (when you get to it) may show you why that is. Other clamp forms work better in wood, as a rule, such as spool clamps and double-screw (or handscrew) clamps.
You will probably need to test the strength of your wood threads yourself, and you may need to adjust various factors (species of wood, orientation, treatments such as epoxy-filling, and probably most easily effective, clamp screw diameter) to find suitable parameters for the clamping you want to do. If you make them in a shape almost entirely seen only in metal (C or G) you may find that the screw threads are not the limiting factor on the thing breaking.