If you think it's hard to break 'bad routines' now, wait until he is 3 and 4 years old. It will be worse--and he'll be stronger, more confident, and determined to get his way.
If you don't want to be co-sleeping when he is 3 1/2 or 4 years old, then you need to fight the battle now. It will be far more excruciating to transition him to sleep in his own bed when he is older.
As for his current bedtime behavior, he may have an ear infection (although I would think he would demonstrate this behavior during the day and not just at bedtime if it was an ear infection). It may be him entering the next phase--the trying 3's--pushing the boundaries, figuring out how to manipulate situations to get his desires (stay up later, attention from mom or dad, getting bedtime snacks, etc.). I found we were most successful at this phase when we followed clear routines and didn't deviate, so that my daughter know exactly what to expect and understood what her wiggle room was.
Good luck!