Raising the head was only for making density calibration prints and contact prints, not for printing the image. Because the image will get bigger as you raise the head, just as you found out.

Non-enlarger bulb is only for "the last option."
If you can use a standard enlarger bulb, use it. 75w seems to be the lowest wattage for enlarger bulbs. After that, use ND filters to reduce the intensity.

As for "the last option," that is for people like ME, who have a Durst L1000. The special enlarger bulb for that enlarger is no longer made, so we have to make do with whatever will work.

Why the fixation on f8?
As other have said, close the lens down as you need to. That is what the aperture control is there for.