Having lived here for several years, I have been to every place under discussion here one or more times. So I have some opinions, LOL As with so many travel decisions, much depends upon your interests.
Dvorak is, route wise, an outlier, but has some things of interest. In addition to the often photographed Roman columns, there is an aqueduct. The main cathedral is somewhat interesting because of its hodgepodge construction with different styles over different centuries. Also in town is the somewhat macabre Chapel of Bones. In the surrounding area are several excellent wineries and a few km to the west, there is a prehistoric stone circle (not as spectacular as Avebury or Stonehenge, but if this sort of thing interests you).
Coimbra is a pleasant university town, but, aside from a tour of the Joanina Library (not as spectacular photos allowed inside) and a tour of the university or botanical garden, tourist options are a little limited.
The Convento do Cristo in Tomar is quite fantastic. The Templar chapel inside is amazing and the Manueline window gives a taste of that architectural style too. (BTW Princ Henry the Navigator - who never left the country - lived most of his life at this complex.) someone also mentioned the Batalha Monastery as a side trip and I concur. (I would skip the Fatima circus unless you are really devout - too commercial for my taste.)
Obidos, is, as others have noted, quite small. (My dentist is in Obidos, so I am there a lot.) It can also be crowded, touristy and parking can be difficult. But if you are determined to go there, not too far away is the Buddha Eden Peace Garden, a wild anomaly you might not expect in Portugal (do some internet searches that include images), that we frequently take visitors to spend a few hours.
A day trip to Sintra is a good idea from Lisbon. Try to get one that will pick you up at or near your accommodations and one that includes a visit to someplace like the Regularia (there are four palaces in and around Sintra from different eras). If you also plan to visit Belem from Lisbon (for the monastery or the tower) consider the Royal Coach Museum as well. Hope this helps.