Boy do I agree with Jackie. Unless you are both hyperactive and just run a lot, then this may be the trip for you. By the time you get to a destination, you will already be working on the next leg of the trip. Please also remember that from SF to Finland, etc. you will experience a 10 hour time change, ego big time jet lag. IF you were doing this from the UK then at least that problem would not be in the mix. You are planning too much in two weeks and when you say 3 days in Finland you will not have 3 days or the one day in Tallinn. Cut the trip by 1/2. Save the trip to Poland and Lithuania for next year and do it in some normal pace. By the time you arrive and find a hotel, eat, etc. you have already lost at least 1/2 of the day, etc. Same with leaving for the next destination, etc.
My friends from next door did something like this a few years ago. They went from Chicago to Paris, got rail passes, and set a tour from Paris, around Germany, then into Swiss, and then Italy, all by train. When finally finding a "hotel" in Paris, he realized that he left his bridge teeth) in the plane WS. No teeth for the rest of the trip. Got totally lost in Germany, and got on a train in Germany to go someplace and got a $50 fine for not paying for a ticket, since that line did not accept the Rail Passes. Spent all of their time looking for cheap places to stay, and the hell about seeing the cities and towns, they had to rest. Finally got to Rome, found a cheap hotel, but upon arrival at the train station in Rome, one of their bags was already missing. Never got it back. They took a trip to Sorento on the way to Pompai. Took the wrong train, and got to Sorento at 6PM, when the last train to Rome leaves at 6:30PM. Did not ever make it to Pompai or saw Sorento. By that time it was a 30 minute look see at St. Peters, and back to the train for a return to Paris. They had a great vacation!!!!! Saw really nothing, spend all kinds of time on trains, lost his teeth, one bag, ran around like idiots looking for places to stay and trying to figure out the various RR schedules, which they kept getting wrong, standing on the wrong tracks, etc.
If you do this trip, please report how it went! Have a nice trip. Also, just to add, AF the last minute in Europe is devestation to your wallet!