Hi Don,
I don't own a Sofrider, but I do ride a Cruzbike. In my experience, climbing hills of that degree can be done, but require excellent technique. You need a buttery smooth spin; mashing will always get the wheel to spin. If your surface is rough and or dirty, it will be tough. You can try lowering the air pressure in the front tire a little. Even ten pounds will give you more contact patch. Then, work on the technique.
Yes, you can climb in a straight line at slow speeds. Again, it goes back to time in the saddle and practice. Your body will figure it out; you need to stop thinking about it so much. I know, it doesn't help the nerves any in the present tense, but it will get better with time.
Starts are much the same way. Practice, practice, practice. I used to wobble on starts, but can take off straight now.
In the meantime, enjoy the ride!!
Mark