I'm just being honest here. I know several families intimately who used that program with their kids. It was far from painless. Their kids were not nice toddlers, and grew to be not nice kids, and not nice teens. For spirited kids, it's wishful thinking that you can avoid firm discipline and have them develop all the right thinking for things on their own through myriad creative reactions to things on your part through the toddler years. These parents were still managing escalating negative behaviors at 4, 5, 6, 7 that our kids nipped around 2.
Some call it lazy to "take the easy way out" and be strict. We call it enabling bad behavior to spiral out of control and wasting tons of time on it if you aren't. Your child should not be talking back, and they should be listening at 3 if you are diligent, loving and firm. It's doesn't take classes and endless repetition.
By trying to do the right thing and be the always nice parent, you may pay the price unless you have a naturally docile child born without the need for discipline (statistically super rare).
Ironically, we use most of the advice in that program anyway, life is always learning and logical consequences, natural lessons in daily life, and we are happy and positively reinforcing, pointing out the right actions, teaching, modeling, and complimenting most of the time. But if you eliminate basic discipline when the need arises, and replace it with diversions and mild "logical consequences" (debatable usually) that the child doesn't even know are consequences, which aren't consistent for anything else, and are not much different form the "happy norm", each lesson takes WAY longer as the child gambles to see what will happen for each new thing. And the stakes are never high enough to just STOP the behavior. I've had people ask me if I used that program, because I'm always having nice positive communications with the kids and asking questions and giving choices. They look surprised to hear they actually had strict toddler discipline.
Some of the parents I know who say that program is working for them like their choice, because they're never the bad guy, but we would find their children's behavior totally unacceptable in our home. Once I got all three of my kids out (3 under 5) to meet my friend at a museum (we drove 3 hours and got there earlier than we needed to just to meet them before another obligation we had), and when we got there, her son decided to throw a fit. She announced they would have to leave to show him he doesn't get away with it-he was getting worse about it- so she had to "really be serious that he missed out on seeing us and doing something fun-the logical consequence" (like he cared!-he wanted attention and he had no interest in the museum because he had never been there). Who got punished here? The kids and I still had fun on our own, but still. He's 7 and he still throws fits (among many other scary things). My 3 year old son would never do that.
If love and logic works for some people great, keep trying a while longer, but at 3, you're in the crucial zone for setting the standard going forward. You're saying your child is still acting out at 3, and I find this is often consistent with the results of this program. Just an outside observation, it may not be you or your child's fault.
If you are not happy with the results, you should follow your gut, and switch to an approach that achieves your standard. Your frustration will disappear as the behavior improves, and your sons pride will be boosted as well.
It's great your husband is actively involved, he needs to take the lead with his son. We liked this book.
www.backtobasicsdiscipline.com