are you talking about the mazda 5 or the mx5 miata ?
either way, when you bump start it at 10mph, put it in either 3rd or 4th, a ton less strain on everything related. Id say 5th but the rpm is simply too low at that speed and could actually cause damage. even 4th is pushing it, but once the car is running you could put it in any gear you like (except 1st, of course)
in my mazda pro5, Im going to be pulling the PS pretty soon, at first, when I EOC, it was really hard to steer, but now its much easier so Im pretty sure its just something you need to get accustomed to.
my PS also comes on whenever I turn the car on, regardless of the speed, it sounds like you might have an air pocket in your PS lines ?