R.S.
Most children show a real interest sometime in the 18 month area, and if you get them quick you can often train them, but if you aren't constant they'll lose interest again. My son was doing really well at that age but we only had a bathroom upstairs and I was very pregnant and then had an infant, and I didn't always take him as soon as he needed, so he ended up being 3 1/2 before he was trained. So give it a try, but keep it up for a few weeks very constantly.
As for the running around peeing on stuff, what is the possibility that the first time he did it, someone (probably Dad) laughed. Now he thinks it's really funny and doesn't really believe how upset you are about it, or enjoys getting a reaction from you. Quit airing his bottom before bath time. It really isn't necessary, as you're gonna get him wet again in just a minute anyway. It would make more sense to let him go without a diaper after the bath (he'll probably pee in the bathwater if you don't have him go potty before putting him in, though. Maybe you could get a special new bath toy that he gets to play with if he goes in the potty before his bath, and remind him each night that he gets the toy as soon as he pee pees.