Hi, Restless,
From the airport to the Se, you can take the metro but it is a long roundabout way. Red line to Alameda, then change to the line that goes downtown. It will take probably about 40 minutes. The airport bus, which I've never taken, also goes downtown.
http://www.yellowbustours.com/en/cities/lisbon/airport-transport/
A cab will take probably half that time, and should cost around 15 euros. But cab drivers in Lisbon, particularly at the airport arrivals, are notorious for the ways in which they try to scam tourists. I go to Lisbon once a year, and I usually take a cab to my hotel. I am obviously a foreigner, but I know Lisbon, and I am usually in a cab whose driver is trying to cheat me.
I just checked the
Tile Museum's website and it closes at 5:30. In the best of circumstances, you would be at the Cathedral by 3:30, walk to the Tile Museum in about a half hour, and still have an hour and a half in the museum. That timeline, however, requires all stars to align correctly, which of course they sometimes do!
I don't know that there are accommodations in Sacavem, but I do know that in Parque de Nacoes there's both a youth hostel and some more upscale hotels. This would be a nice place to spend a first night in Lisbon, IMO. Of course if you walk to Sacavem, you could hop on the commuter train back to Parque de Nacoes to spend the night and then return in the morning.
Hope this helps, bom caminho, Laurie