Firstly, be aware that there is no direct train service between Lisbon and Seville. One has to travel to Madrid and then to Seville.
Indeed the train service between Lisbon and Madrid is, at present, restricted to one overnight train per day.
Have a look at the following article on my blog about this!
http://barlaventostravelblog.blogspot.com/2009/03/trainbus-sevillespain-to-lisbonportugal.html
To be honest, if you want to do Seville from Lisbon, I do recommend the bus. The cost is only circa only € 35,00 one way.
Current Timetable:
LISBON Sete.Rios SEVILLE 09:00 17:45 61,00 Thursday to Sunday.
LISBON Sete Rios SEVILLE 20:45 05:15 61,00 Daily
You refer Evora. This is at a dogs leg from the other towns you have mentioned. It might be better left for a subsequent trip.
You are going to be hard pressed to do Lisbon, Sintra, Cascais, Obidos and Fatima in six days.
You need to allow at least 2 full days for Lisbon, a day from Sintra, Cascais and a day each for Obidos and Fatima.
To do all the latter two using buses is preferable as the stations are a ways from the town.
If you search my blogs under the town names, you should find more snippets and info which will help you.
Please email me about any specific queries that subsequently arise.
http://barlaventostravelblog.blogspot.com
