A general comment here.

I have long considered mathematics to be analytic, so I have never agreed with Kan't "a priori synthetic."  However, given that Kant's definition of "analytic" was different from what is used today, I'm not sure it is worth arguing.

Quine obviously disagrees.  His "Truth by convention" was an attempt to prove that mathematics is not analytic.  I was not persuaded.  I thought it a plausible argument against formalism as a philosophy of mathematics, but it has little to do with the way that mathematicians think.

On the other hand, that brings up a different point.  Maybe a proposition can be analytic for me, but synthetic for you.  This would be because we have subtly different meanings for the relevant terms.

As for Bolzano:  I see him as using what I would consider a geometric methodology.  I would put ideas such as continuity into geometry.  To my way of thinking, geometric methodology is a source of new concepts and of analytic propositions related to those concepts.

Regards,
Neil