It's a little hard to tell by the pictures but I would use something in the area of 45 deg. angle for the handle.
Also larger as opposed to smaller bearing/wheels might be in order. In the case of checker plate flooring you may not always have a smooth surface to roll on. Also a way of "tapping" the leading edge of the device under the load might be a good idea.
A good crow bar modified might be a starting place. I've spent 35 years as a mill wright positioning heavy equipment so I have a pretty good idea about what you're looking for.