questions about L4 (1st gen. Auto 4x4)

I'm not sure if these things are normal or not:

1) When in L4, if my speed gets up enough to cause the transmission to shift to second, there is a strong lunge.
I know you want to use L4 at speeds under 10 mph. But at times, climbing a steep hill, the incline will level out some and let my speed jump up enough to cause a shift. When this happens, there is a strong lunge or jerk. Obviously I could just keep the trans shifter in 1st gear (L), but then I am limited in speed as conditions change. Which brings me to number 2.

2) I cannot ever shift out of L4 unless the truck is completely level. I have a manual J shifter, and it will not budge at all unless my truck is level. And sometimes its just hard in general, to get out of L4, and I have to drive the truck a few feet in either direction, put it in park and try again. Kind of quirky.
This creates a problem when I am climbing a hill on a dirt road or trail, and the steepness levels off some. I want to get out of L4 so I can travel faster, but am unable to stop the truck on the incline and shift out of L4, as its not a level surface. Or if heading down a dirt road and suddenly pavement starts on the incline and I want to shift out of 4wd to prevent binding. Its not possible because of the incline.

Can I use H4 at speeds under 10 mph if only for a bit? Or should I only shift into it if I'm already traveling above 10 mph? Like say, at the bottom of a hill, while stopped, shift into H4 and climb the hill, going through first and second gears, and eventually traveling at 15-20 mph?

I love my 4wd.