This site indeed contains the alphabetical list of people who took part in January Rising. The list is based on Russian archives and unfortunately I don't know where a they are located. I have had a quick view at entries concerning the Dowiat family. There are several men with this name mentioned. I found the one you are talking about:
Nikodem Dowiat, nobleman of Wilno province for his part in the uprising was deported by the Russians to Mariinskie (probably it is contemporary Mariinsk in Kemerovo region, half way between Novosibirsk and Krasnoyarsk.) He is mentioned as living there in 1868 and the record also states that he had no family at that time.
The other Dowiats are from the Kowno area, if you would like to know what the Russian records say about them I can translate it for you. The family is also mentioned on this site in the discussion section, but as I have just registered here, I am not allowed to see this content yet. Have you by any chance seen those topics on the current site? When I gain access to more info from this site I can find out whether the members of this forum have any valuable information about the Dowiat family.