Uber and Free Now both worked well for us in Lisbon in July as long as your cell phone will work in Portugal. Only catch is in some busy places in downtown they have designated pickup spots (but they can drop off anywhere). If your hotel is in one of these zones, a taxi out will be a better option if you have lots of luggage.
Bairro Alto is the center of Lisbon night life. You can easily walk that entire area and the adjacent Praca de Commercio / Rossio districts.
Sintra / Pena Palace / Moorish Castle are some of the very best Portugal has to offer. If you feel like your last trip checked those boxes, then I might concentrate more in Lisbon itself. St George Castle, Geronimos Monistary, Royal Carraige and Naval Museum, Belem tower, wandering around the Alfama old town. Weather in January may be wet and cold which could affect your touring plans in terms of outdoor activities.
If it wasn't winter, Evora is a two hour train ride and is a walled city dating back to Roman times complete with Roman temple and intact medeival city walls. It's very much a pedestrian experience though and liable to be very cold in January.
I lived in Portugal previously, it's a wonderful place.