I tell you, 5.5 and 5 hours sounds too long for this age, particularly if teeth may be involved. At that age, most are doing closer to 4.5-5 hours. I think I might shrink that 1st A time to 5 hours and see what happens. And absolutely experiment with some Motrin -- one dose before nap ought to give you some info.
I would be careful with wind down at this age. as PP said, TV depends on the kiddo. For my kid ANY kind of TV show was too stimulating. He's a touchy/textbook bub. (you might take the toddler quiz at this point if its been a few months since you've done so -- now you might get a different personality type!). What we did at 18 months was keep wind down to about 15-20 minutes. We would say night-night to things/objects in our house and out the window as we made our way to bed. We had to do baths much earlier in the day b/c a bath would get him overstimulated as well. Then it was jammies and stories in his rocker. My son still had a night time bottle at that age, so we had bottle while reading. Then we would turn out the lights and sing 2 songs while in the rocker. At that point he'd be pretty relaxed and into the crib he'd go!
If you do books, I'd keep it to 2-3 short board books. That's usually enough to get LO relaxed, but not so many that they get restless.
