Dude you're rushing it. From your list I gather that you're probably not much into hiking, taking the scenic route, gorgeous landscapes and rural towns and villages (God, you find the BEST fucking bread in little french and spanish villages. They usually still have a genuine baker with a fucking wood fired oven.), so you'll probably be fine with your pace but you're cutting out the best part imo. Also since most of your vacation will be spent on planes probably, be prepared to be exhausted and tired a lot of the time.

As fas as recommendations go, you have a tight schedule so it would be good to know what you're interested in. Is it just nightlife? Or are you interested in landmarks and cultural stuff too?

Paris alone can easily be a week long trip, if you even want to get close to seeing all the worthwhile stuff and have a chance to really dive into the nightlife.
A day stop in paris is only fine if you're spending three weeks in the country and have been there before imo. You need about a day for versaille, same for the Louvre, while half a day will do for the Eiffel Tower (I'd actually recommend doing it right before dusk, you get to see the city by last daylight get to watch the sunset and the gorgeou city by night), At that point you haven't even seen the catacombs or champs elisees or any of the city really, or had delicious macarons and ice cream.

Do the croke Park skyline tour in Dublin.  

Have fun drinking.  Good pubs, buskers (they have a games room downstairs,  table tennis,  pool etc),  the living room.  

If you want somewhere full of the most drunk students and young people ever go to coppers. But trust me you'll want to be very drunk to enjoy it.  They open till like 6am so maybe go there last. 

What are you exactly visiting in Romania the 30th of October? Also, the Dracula Castle is a good choice even if Peles would have been a better choice imo.

My advice would of been to avoid the big cities. From my experience, once you've been to a couple of big cities you've been tonthen all, all culture and native way go out the window. You'll see the same shops, the same advertisements the same vehicles.
But that's just me i guess. I'm more into trekking the wilderness parts and meeting people in smaller places, I find it's a much better experience.

Stay away from people trying to sell you stuff on the streets. I've noticed these people in italy and france. They don't exist in germany, though.

And wtf? No Berlin? The future capital of Europe :P

There is a guide I used on my trip to Europe a few years ag. It was actually on TV, and although it was up on youtube briefly, it's been taken down. :( I have the full guide on my laptop, but am a bit leery about uploading it. I hope this clip helps you out im some way.

Dublin? Paid -  Croke park and/or aviva stadium, Guiness brewery. Just countless things to do really. So many wonderful pubs, cafe's, bars etc. Just wonder around the city. I'd highly suggest a bus tour out if you have a few days. So much stuff to see around the country. The likes of the ring of kerry, dingle peninsula or cliffs of moher, newgrange (5500 year old pyramid style structure.)

Free - Dail Eireann + a spate of free museums together, Trinity College, Dublin castle.

The economy is doing well right now so hotels will be expensive. Try hostel shining dublin, for very cheap rates if that suits you. 

You'll find it hard to see most of many of these cities in a few days. I would have planned maybe at least 5 days in each, or split across numerous trips. European cities have a lot more depth than American cities if your interest is in culture or history. You could end uo looking at all the wrong things and have a dull trip to any one city because the trip is so short, and you may miss all the good stuff in an unlucky way. It does sound amazing though! Stock up on lucosade and drink plenty of Guiness/Beamish/Murphys and you'll be fine ;)

When eating in Rome, try and go to Testaccio, the culinary area. It's an artificial hill built from centuries of discarded clay amphorae.
I personally recommend the restaurant "Il Bucatino".

In Paris Rue de la Huchette is a pretty safe bet, and la Braserade there serves typical French foundues and it's quite great.
Walking along la Senne is also quite fantastic, and the ideal place to get a few souvenirs or books for cheap.

If I had any suggestions, try to plan your visits ahead of time, but leave some time just for walking and exploring.
Going from museum to museum on a schedule can be very stressing, so idle breaks help avoiding it all becoming routine. It also helps in scouting out restaurants before dinner.
As a general tip, avoid restaurants near city centers, or places full of tourists

I think keeping a journal to write your thoughts is also a great idea, even if you do it every couple days or so.

Dude, you're cramming in too much! That list is like startung in Seattle, going to LA, to Houston, to New Orleans, to Washington, to Chicago, to New York or something. Europe isn't THAT small. You won't be able to see much of any location.

Nu tip is to avoid the usual tourist traps, don't go to the Louvre in Paris; you don't wanna stand in line for two hours when you have so little time in each city. Maybe just wander around. Or make a short list of places you wanna visit and see in each location.

When I was in Berlin, nobody tried to sell me stuff, but there were a lot of people who tried to make me sign a paper and donate money.

OT: The London Dungeon is very fun and entertaining. Actors show you the stories of Guy Fawkes, the plague, Jack the Ripper...