Does anyone know how to take apart this hub to do a single speed conversion

Are you sure you need to take it apart for a single speed conversion?

Soaking it in WD-40 or such, and then leave it for a day before trying again.

You could maybe try to set the wrenches close together, and then squeeze them together with both hands.

Another option is trying to find some longer wrenches or pipes to try and get some leverage.

You could also try to apply some heat, so that the metal expands.

Here's a video of a guy opening a similar hub:

Assuming this is a standard freewheel hub there should be no need to disassemble it, since you can simply remove the freewheel and install a single-speed freewheel made for this replacement process.

To remove the old freewheel you generally need a freewheel tool that matches the existing freewheel's design. There are a half-dozen different schemes for this, depending mostly on the brand of the freewheel, so you may need to visit a bike shop to get an exact match.

If you really want to disassemble the hub itself you do it one nut at a time, starting from the outermost nuts and working inward.