Setting tab order in Acrobat is pretty much a simple click process. There might be an Adobe JavaScript out there to help with this, but I haven't found it yet. I think you have the right idea. Simply right click the first field in the tab order, and from the resulting menu, select "Set Tab Order". Then, just click through the fields till your order is set. If you're like me and you get messed up in the process of clicking through your 100 field page, simply click the last field you left off at (say the 50th field), right click and choose "Set Tab Order" again, then hold the CTRL key down and left click that 50th field. You can then click the remaining fields from there out and they will start in the right order (51, 52, 53...)
Hope that helps.