There certainly is a lot of information here. I would just like to add that it's great that you are so determined to devote your time and energies to achieving this worthwhile goal. You are obviously a dedicated mom.
Something to keep in mind for this process is the developmental stage your son is in. He's doing more than just growing taller. In his body several billion changes occur every day. The bladder is growing at its own pace, and so are the number of nerves which provide cues to the brain to say "It's time to go." Training is woefully more than an education process, it depends on your child's physical growth as well. What's more, that part of the brain which controls muscle function of the bladder sphincter, the voluntary and involuntary coordination which are necessary for potty training is still becoming coordinated and fine-tuned. Please bear this in mind on those frustrating days. It's not simply a matter of willpower and determination, but also a physiological process.
One of your readers touched on this when she said to check him when he first wakes up to see if he's dry. By this, she means, is his bladder big enough to hold all his urine through the entire night. This is a good indicator that at least the bladder is becoming ready.
Another thing one of your readers mentioned is that children have different ages when they seem to be capable of doing this. It really is a physiological achievement, as much as a learning one, and only a part of it is within your son's control.
My mom was old-school as well and felt that children SHOULD be trained by two. Back in the 70's, it was like a sign of your parenting success if you did or did not have your child trained. But they did not have such things back then as access to the broad range of knowledge that we do today with groups like this, and the internet, where we can look up information for ourselves and not simply rely on our check ups at the pediatrician's office. I was urged on my my mom as I taught my daughter (We began at 19 months for her.....and she wasn't trained for another 14 months....yes, I put my time into it and was dedicated just like you).
For my two year old son, I continue to ask him if he wants to go potty when we get up in the morning, because he is dry, but he's not interested. He's very determined. I know that trying to force him when he's not ready will make it harder down the road by creating a potty "aversion" so I'm just waiting it out and trying not to stress about it. If it's going to take him as long as my daughter (and different kids have different timelines, even within the same family) then it is, in fact, less stress on me to not force him through it.
One of my girlfriends SWEARS by the candy method. Another one uses stickers and singing and clapping. Different things had different effects on my daughter depending on her mood that day. Sometimes she was buying it. Sometimes not. Ha ha.
I'm so incredibly excited for you with your new baby on the way. Congratulations! I'm wishing for a peaceful, stress-free journey into mothering with two!