You're right. The lies will NOT stop. You're also right that you cannot have a relationship with someone you do not trust. If they aren't willing to get THAT much straight, then they are not the one for you (and that means they are NOT your "best friend"), and (yes, you're right again) you'd be better off elsewhere. You AND your daughter.
Remember, you can love someone and still not be able to be with them. Love is only one part of the equation to a good relationship...and when it's countered by everything else being missing...well, it's time to get out.
Sure it's hard....and it won't get any easier. However, like most things, being hard just means you'll appreciate it THAT MUCH MORE when you make it happen.
Cut yourself free, spread your wings, and soar, darlin'. You know who you are.