Re: How much oil and dipstick reading.
I believe we have the same motor and I have experienced the same with the installed pump being incapable of getting out all the old oil.
I pump until nothing comes out, and then add a quart or two of fresh oil. I wait a few minutes for it to drain to the bottom of the pan and pump that out. I repeat the process one more time before adding and topping off the oil. I have found this makes a huge difference in the length of time the oil starts to look dirty. I do the same with the Onan.
I have no idea if it is worth the expense of the extra oil but the way I look at it oil is cheap compared to a new engine and I sleep better.
All the best,
Cruising New England