Another brush that works also is the Pattern brush
Drag and drop your shape inside the swatches panel
Then crate a new brush and select pattern brush
if you want more space between shapes, you can edit the pattern
Select te pattern tile tool and increase the size
Let me know if you have more questions
I don't understand what you mean by the start and end points moving/not moving. The start and end points of the original blend are determined by the center points of the starting and ending objects. When you replace the spine, the endpoints of the spine determine the new location of the centers of the starting and ending objects.
The bottom line is that when I choose to blend from one shape to another, I expect the first shape to stay exactly like it is and I expect the last shape to stay exactly like it is. Period.
Even if I blend along a spline, the start and end shapes should not change. If the start point is offset from the start of the spline path than the offset becomes another value to translate between the two shapes, but point A should not move.
I believe you will be fine if you prepare the Spine path by using Object>Path>Add Anchor Points until you have enough segments to ensure an even Blend; you may go back and forth between adding Anchor Points and replacing Spine (Ctrl/Cmd+Z is your friend) until you are satisfied.