Thanks for showing us this. My baby brother had an elephant toy similar in shape to this in 1952, and I think it would be fun to make one for my little grandson.
I'm sorry I don't really know how to answer your question about the seams because I haven't worked with a Janome, but you do need to use the seam allowance stated in the pattern or parts may not go together correctly. If you can move your needle to the left, you may have a foot that has the correct distance at the right edge. When I want to test the distance I like to sew a few stitches along the edge of an index card. Then I can write on the card what my settings were for future reference.
Using the elephant as a doorstop will be complicated by it's high center of gravity. Maybe you could wrap a brick with batting and fabric and attach the elephant on top of it.