"But I also think abortion is a lesser evil because I think an established life has more worth"
Ah this is where a lot of the difficulties stem from.
Many cultures and societies do not believe a woman has much worth.
Taking an approach that quantifies the "worth" of a person is a minefield, given that all societies explicitly or implicitly place different value on different types of people - sex, wealth, age, disability, race, education level, all sorts of things go into judging how "valuable" a person is.
How much value is a profoundly disabled women, compared to a non disabled foetus in her womb? For instance.
These are the sort of questions Richard Dawkins and his ilk enjoy pondering, and are grossly offensive, quite frankly.