I really don't think that aggregate GPA is all that important relative to other factors. Your grades in Math look solid.
I would strongly discourage you from sending a letter of recommendation from a philosophy professor. Regardless of what he/she says, adcoms are looking for someone who can vouch that you can survive the first year and/or show promise as a researcher. I would suggest getting one from a professor of a proof-intensive course that you have taken.
I don't really think that a MS Statistics or post-bac is necessary or an optimal use of your time. Rather than taking more courses, I'd suggest doing RA for a year or two (and hopefully get a stronger letter of recommendation from an academic economist).