1 & 5. 1 country per week is a reasonable rule of thumb, however this could be tight for 4 weeks because of the extra time involved in getting to/from Spain, to/from and around Greece and to a lessor extent to/from Italy.
2. Your order of countries will work, but I’d seriously look at the cheapest transatlantic flight options before deciding on an itinerary. Look for open jaw flights to avoid backtracking.
3. What does the trip planner recommend for a railpass? Have you looked into cheap flights for some of these e-x-t-r-e-m-e-l-y long treks? You might find flights that are cheaper than using a day of the railpass.
4. I would limit overnight trains and overnight ferries to 4 (5 or 6 if you get a cabin on the ferry), so you will be spending most of your time in hostels. I would look for cheap flights instead of overnight trains as an option for some of the longer treks.

I did these same countries last summer (as well as Croatia). I think 4 weeks would be ideal. Looking into flying open-jaw- maybe into Athens and out of Madrid? You could start in Athens for a couple days (2-3) and then ferry to Santorini for 3-4 days, then either ferry back to Athens and fly to Rome, or fly from Santorini to Rome. We opted to fly because it saved us so much time (left Santorini at 6 am, brief layover in Athens, and arrived in Rome at 10:30 am, with the whole afternoon to see Rome), but it was a pretty pricey flight.

Spend 3-4 days in Rome, then train to Venice to 2-3 days. I’d maybe add a stop along the way, either in Florence or Cinque Terre for 3ish days.

Either train to Paris (overnight is an option), OR I’d spend 2-4 days in the French Riviera (we based in Nice) before training to Paris for 4 days.

Then, overnight train to Barcelona or look for a cheap flight. Stay 3-4 days, before train or bus to Madrid for 3-4 days. Toledo is a great day trip from Madrid. Then fly home from Madrid.

That’s about a week in each country, which is fine (with maybe a little more time in Italy, if you wanted to add a stop. Trains are very inexpensive and those places are only a few hours apart).

I’m not a fan of overnight trains so I would avoid too many of them, though the options I mentioned (Paris-Barcelona; Venice-Paris if you skip other parts of France) may work well for you. Cheap flights are also a good option- keep in mind a flight takes min. 5-6 hours and there are additional expenses (getting to/from airports, etc). Check out skyscanner.com to see if flights may work for you. Don’t plan on getting much sleep on trains.

Otherwise, stay in hostels! They are great places to meet others, and with earplugs, I always got a good night’s sleep. I can recommend some very good ones for you, if interested.

Thank you both for the invaluable advice! A couple more questions: which treks would be the most worthwhile for the flight? I found a $75 flight from athens to rome, is this a good deal? And in terms of overnight trains, what about them don’t you like?

I forgot to ask if it is safe to travel alone as a woman?

$75 Athens-Rome seems like a good price to me (though I am not an expert on flights at all). Keep in mind you would need to ferry from Santorini back to Athens, stay over in Athens, and fly out the next day. That is why I ended up taking the much pricer flight from Santorini to Rome, because I didn’t want to lose that day just traveling. Just something to keep in mind.

I’d also fly Paris to Barcelona.

My dislike of overnight trains is a personal preference. I can’t sleep on trains/buses/planes; even if you don’t have this issue, you likely won’t get a full nights sleep. You’d then arrive in your new city tired and cranky, instead of eager to explore. It just doesn’t seem worth it to me. Also, if I was traveling alone I would not be comfortable on a night train. Keep in mind this is purely a personal preference.

You’ll be fine traveling alone as a woman as long as you exercise simple common sense. Research hostels ahead of time and read the reviews, making sure it’s in a safe neighborhood. Don’t drink excessively. Take cabs back to the hostel instead of walking back alone if it seems unsafe. Wear a money belt and just be aware of your surroundings.

I would definitely fly from Rome to Athens. You’d spend 1/2 day on the train from Rome to the ferry port, overnight on the ferry and then nearly 1/2 day getting to Athens.

I don’t mind overnight trains, but you often don’t get a good night’s sleep. I find it disorienting to arrive in a strange city at morning rush hour. Often you can’t check into hotel or hostel until late afternoon and what you really want is a shower and a nap. It can be surprisingly hard to find breakfast in a strange city. I suggest limiting to 1 a week. I have never had any trouble sleeping on a ferry when I had a cabin, so I don’t feel the same way about that. However, it can still be tough to deal with finding breakfast and getting oriented in a new city before I’m fully awake. I feel the same way about the hurry up and wait nature of flying — getting to the airport, arriving too early for 2 hour advance check-in, security hassles, flight, getting to town from the airport. I limit those to 1 a week, too.

Use the German national rail company website for train schedules: www.bahn.de will get you started (I’m not good at copying links on the IPad). My rules of thumb:
Train ride 5 hours or less, take the train
Train ride 5 to 7 hours, take train or fly, whichever’s cheaper and/or less likely, schedule-wise, to screw up a whole day. A one hour flight at 1:00 PM screws up a whole day of sightseeing, while a 6 hour train ride leaving at 4:00 PM leaves you more than 1/2 the day to visit sights before you go. If night life is your thing, look at the reverse.
Train ride over 7 hours, fly or take an overnight train unless the flight is prohibitively expensive or the overnight train involves connections that will further mess up sleeping.

thank you for the help!

my friend and i purchased a ticket from rome to palermo, and now we realize we need a route from sicily to athens or a greek island. what route would you suggest? ferry/train/flight? we’re thinking cheap price but not at the cost of wasting so much time.