Its funny since I was just observing today the differences between the two sexes of bufo americanus. I can't say for sure. I'm no expert at all, but since my toads have grown larger its been easier to tell. (6 of them are 4 years old and 4 of them are 3 year olds.) If I still had my digital camera I'd take a side by side photo of one of my females and one of my males but its broken and needs to be fixed.
The thing that sets them apart- other than the dark throat and the whole ability to make a chirp- is their upper arms. I notice that my female's upper arms (sorry, I don't know the real technical word for that part of a toad's body!) are smaller, more daintier than the males. The males seem to have a "muscle-man" look. Also, the males back feet seem larger and longer than the females. Males also have the 'nuptual pad' which I mistook for dirt the first time I saw it on my largest male toad. It looks like dried mud on the tops of their "thumb" and "forefinger" (Yes, I know those are human terms but I think y'all know what I'm getting at!) I know that when my toads were about the size you described yours it was very hard to tell, so it may just be that you will have to wait 'till they develop more. I also noticed that the females look different from behind. Males tend to have this prominent 'buttbone' that juts up and out more. (I hope at least one other person out there agrees with this, otherwise I'm going to look very stupid!)
You said something about the warts on the back legs... I didn't know that before, nor did I notice it but once I read that, I somewhat remember not seeing larger warts on the back legs of the females and I do remember seeing large more conical warts on the back legs of most of my males though. I'll have to go take a closer look.
A couple other things: my males started to chirp around after they grew more than about an inch and a half. I've noticed both my females and my males grasp/hug, though the males do it far more often. Very rarely, like maybe twice or 3 times, I've only noticed my females do this when it seemed like they were loosing their balance and/or needing to hold on to something to get to wherever they were going.
HOpe this helps! -Laurah