If I get lucky and order in advance the needed tickets AND get the cheapest tickets, point to point is the way to go.
Well, taking into consideration your itinerary it seems that purchase in advance & discounted tickets aren't always the best solutions for you, so you don't really need to tie yourself in all the journeys, because you easily can still have some flexibility even without Eurail pass. But let's look step by step:
Berlin to Stralsund: here you not necessarily need to "hunt" for discounted tickets, because German Railways (DB) offer pretty good local train passes. In case of this journey ones to consider are Schönes-Wochenende-Ticket (for weekends) or Quer-durchs-Land-Ticket (for weekdays). Both passes allow unlimited journeys during one day all over Germany for groups up to 5 passengers, and best thing about both passes is that they can be bought even before departure, so such passes are perfect for day trips like Berlin-Stralsund-Berlin. Quer-durchs-Land-Ticket for two passengers cost just 50 euro, while Schönes-Wochenende-Ticket even cheaper - 42 euro. As result both of you can travel Berlin-Stralsund-Berlin for not more than 50 euro and without any need to buy anything in advance. The only minor inconvenience is that such passes are not valid for IC trains, so you'll have to use slight slower regional trains (although in case of Berlin-Stralsund difference is just extra 15-20 minutes). More info on Quer-durchs-Land-Ticket & Schönes-Wochenende-Ticket you can find on our
Germany pageBerlin to Potsdam: Potsdam is really close to Berlin, so even full fare standard tickets are very cheap (3,1 euro one-way from Berlin Hbf to Potsdam Hbf), so definitely spending Eurail pass day on daytrip to Potsdam is useless, just buy regular ticket before departure and don't worry about the price
Berlin to Munich (with CNL train): while here because of a long journey indeed purchase in advance of the discounted ticket is a reasonable choice, but I guess you won't need a lot of flexibility here, thus buying Berlin-Munich ticket in advance isn't that big of an issue
Munich to Dachau: and again, as with Berlin to Potsdam, Dachau is not far from to Munich (just 11-21 minutes by train), so standard full fare ticket is your choice. Plus here you can get MVV (Munich Transport and Tariff Association) which will cover not only journey to Dachau, but also public transport.
Partner Day Ticket from MVV cost 13,6 € and both of you can ride as much as you want in Munich and around
Munich to Salzburg: again, local German pass is your solution here. In this case best choice is so called Bavaria Ticket (Bayern-Ticket), idea is the same as with Quer-durchs-Land-Ticket & Schönes-Wochenende-Ticket, but here it's valid only in Bavaria and some border stations (including Salzburg). So for 26 euro (price of Bavaria Ticket for two passengers) you can travel Munich to Salzburg without any need to buy tickets in advance, show up at the station & buy your Bavaria Ticket via DB ticket machine, that's it
Salzburg to Venice: due to long distance here a good choice is to buy discounted tickets in advance. Btw, we have a step by step guide on how to purchase tickets via Austria Railways (OeBB) website -
http://europetrainsguide.com/Advice/How-to-Buy-Train-Tickets/Austria-OeBB.htmlVenice to Florence: two relatively cheap options here: a) purchase in advance via
TrenItalia or
Italo websites discounted tickets for direct high-speed trains (start from only 9 euro) or b) don't bother with in advance purchase, but simply use slower, however much cheaper (if to compare full fares) regional trains, for which standard fare ticket Venice-Florence is just 15,85 euro (and you can buy such ticket even 5 minutes before departure)
Florence to Rome: as in previous case, in order to travel cheaper you can either buy in advance discounted tickets (again start from 9 euro) or opt for slower regional trains (standard full fare is 20,25 euro) and don't think about buying tickets in advance