I think right on target with your ideas. Three thoughts came mind:
1) constipation or urinary tract infection can make it uncomfortable to go; conversely,Urinary tract infection or diarrhea can make it difficult to hold.
2) as we scurry/nest for the impending #2 child, it's natural to give less attention to #1. Kids at this age like attention. ANY attention even negative. If you up the attention generally (sounds kind of crazy but goes like this "oh look how patiently you waited for me to get that book down for you ... How helpful you were when you carried your plate to the sink .... Picked things off the floor that mommy can no longer reach, etc" LOL. At first you'll feel like you sound wired, but pour it on thick so your child doesn't seek attn via toileting.
3) could be asserting power - use reverse psychology - act like you "don't care, but if you want to be able to go to school, swim in pool without diapers, etc ... You would have to be using the toilet all the time." That puts internal pressure on the child, not your external pressure, so there is no struggle between you. Now you've become the ally. You might even hear things like, "mom can you help me learn to use the big toilet all the time?" Really!
4) Peer pressure at your house- the BEST way to apply pressure is by having other kids come over and use YOUR kid's training toilet. Let your child watch even (not at all wierd @ this age). Go bananas with praise when that child does. Also feign talking about it with their mom within earshot. "oh mrs. Smith little Mary did so well using the toilet while she was here today -- she used it 2 times!" never mind if two more times were accidents -- praise the positive.
5) preschool - do it!! Starting at 2.5 years. I recommend for Lombard area - Co-op Nursery School ###-###-#### ext. 14 @ First Church of Lombard. Don't have to me fully toilet trained -- but willbe I guarantee by end of school year! The also have a one day/week program starting @ 14 months.
6) reward initiative - lots of books say don't reward with food - nonsense!! Its immediate and concrete. Got this idea from neighbor and it works: put two jars visible but inaccessible to child. One is m&m's,the other 1" red liquorice pieces. (Use whatever hits a chord with your child.) child gets one from first jar if they are able to make #1/#2, but (here's the genius) also one from 2nd jar if it was THEIR IDEA. So even if the child goes in and tries and it was their idea they get the second jar. Again, this takes away the struggle because they are pitted against their own interest in treats, not what you want (they think! ;-)
Good luck and as they always say, "don't worry ... Almost nobody ever goes to college in diapers." There really is an end to this phase.