I can't seem to figure out how to do a direct pattern stamp in Krita, working similar to the way Gimp and Photoshop do it. I don't mean clone stamp but directly painting a pattern from a pattern, which can be full color. Does this exist on Krita?

Another issue I have is drawing straight lines. I know how to use the line tool, but I saw somewhere the hotkey 'V' can do straight lines with the freehand brush tool. It doesn't seem to work for me.

This ruler tool pops up and I can't seem to get rid of it, and instead of going back to the free hand brush tool the Shape manipulation tool defaults and mess builds very quickly. Soon there are numerous ruler that seem to appear and won't go away. I basically have to close the image and start over. Since I'm not sure how to use this ruler tool yet (I guess it could be very helpful if I knew how to use it), I have to be very careful not to press the 'V' hotkey.

What I am doing wrong here or is there a video or something that explains how to do something that seems to me so basic and should be easy?

That sounds like somehow the V hotkey got assigned to the assistant editing tool. You can change it in the settings.

As for the other f5->pixel brush->source->pattern.

Oh that is so awesome! I missed the pattern option, although I have been using the gradient and source. I was thinking, man if I could only pattern stamp that would be great. Having to switch between Gimp and Krita was getting a little tedious.

While TheraHedwig did indeed answer my question, and thanks for that, I notice a problem with using a pattern as a brush source:

On the left is a selection I filled with a pattern. On the right is a selection I painted with the pattern source. It actually works fine until I enable pressure settings for 'size'