I have very similar situation. I have a 2 year old and should be having my second baby next week. My daughter unfortunately wont do a crib or any confining items, been that way since she was born but she knows she cant get out of bed at night. She will scream and scream its gone on for up to two hours. I found what works the best if you can is not to let her nap past a certain time, I make sure my daughter is up from her nap at least 5 hours before bedtime and after dinner is taken care of we do some running around/tickle time, then slowly switch to watching a cartoon and coloring for a bit or reading some books to calm her down. If she gets up during the night I think the best you can do is reassure her she is ok or let her soothe herself but you should only do one so she doesnt get the idea that if she cries for just a couple more minutes you will come in. Hopefully this helps some good luck.
To answer your question about a time limit to let them scream it out...We were told by our doctor there isn't one. As long as nothing is wrong, spoiled diaper or such. Kids can be incredibly stubborn. If she knows eventually you'll come in there, why would she ever fall asleep on her own??? You just have to be consistant. If you're going to let her cry it out, you have to every night. It will take a few nights but, she'll eventually decide it's not working and give up.
I have a 2yr old and the "night-time" routine has been the same since she was about 7months old...Dinner, playtime, bathtime, then a calm activity, read a book, cuddle while singing one song, then bed. She falls asleep on her own within ten minutes and sleeps straight through for at least 10 hours.
The only exceptions have been if she's had a bad time teething. And even then a short song and she would fall back asleep. Hope this gives you some ideas!