Stick to it mama! It's only a season (though a stinky, exasperating and exhausting one I know!!!) and sending the mixed message of going back to diapers each time it gets tough it likely VERY confusing to him and not helping him learn what it is you are trying so hard to teach him!
I don't say this to brag, I truly do want to encourage you that it is possible. I have potty trained all five of my kids (who are all 6 years old and under, including twins) and I have taken the route that the earlier the better, for them and for our whole family! I like to say it's less like potty training them then it is "un-training". Our babies show us signs of having to go potty straight from the womb just like they show us they are tired or hungry. The vast majority of parents have just ignored these signs and trained them by default that the diaper is where they are to put the pee and poo and by 2 years old they have learned this lesson so well that it takes a decent amount of work to unlearn it! My son is 11 months old now and has been going on the potty since he was 6 weeks old. He is just now learning to give me the signals of blowing his lips when he has to poo. Certainly this has been a lot of mama-training but I find it is not any harder than changing and washing all those stinky would be messy diapers! I still leave them in diapers when they are babies but once they are two, off they come. By that point they have been going on the potty so frequently and often have learned to tell me or try and climb on themselves that the step to undies is fairly unremarkable. I kindly disagree with most people who say you need to follow your kiddos lead, you are the mama, they follow you! :) You teach, they learn. Certainly we all learn wonderful things from our kiddos as well but in areas like where to put their poo, I suggest you take a deep breath and stick with it, your little man is smart, he WILL learn if you don't give up and in the meantime, yes, it is "mom-training", but it won't last forever. I know it is lame but you will be SOOOO glad in a few weeks when you can go in public again without worry of an accident! And maybe your hubby can have a professional carpet cleaner stop by when it's all over for a little "good job mama" gift! :)
I agree with the naked posts! Just take off the clothes, grin and bear it! If it is nice outside and you have a yard trying playing outside naked a few hours a day teaching him to pee on a tree, so fun! And you'll get your Vitamin D as a good side benefit!
Make a big deal out of the successes with your praise, encouragement and excitement and never shame them. But I would avoid too many complicated systems of rewards and such. They need to learn where their waste belongs, it's that simple. It is a basic skill and we don't give sugar as a reward when our kids learn a basic life skill right? First time they climb the ladder at the park? When they learn to write their name? Count to ten? You get my point...
Whatever you decide to do, try not to worry and just enjoy your little people, they do grow up too fast! You are a great mama and how long our kids are in diapers is really not all that important in the end, just do what you need to do for your family and your sanity! Cheers!