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How long I think you need to do these cities as a first time visitor is:-

Dublin 3 days
Belfast 2 days (but I'd skip it due to your very heavy itinerary)
Edinburgh 2 days
London 5-7 days
Paris 5-7 days
Antwerp 1 day (it's another candidate for skipping)
Amsterdam 4 days
Copenhagen (another candidate for skipping due to geographical location - takes ages to get from Amsterdam to Copenhagen unless you fly) 2-3 days
Stockholm (same as Copenhagen - consider skipping) 2-3 days
Berlin 3-4 days
Vienna 2 days
Prague 3-4 days
Salzburg 2 days
Munich 3 days for the city + 1 for Neuschwanstein and another day for Dachau
interlaken 0 days (it's not nice, go find a nearby village) 2-7 days depending on how much scenery you want
Venice 3 days
Ancona Family, OK, 4 days
Rome 4-7 days
Florence 3 days
Barcelona 3 days
Pamplona 2 days
Madrid 3-4 days
Ibiza (skip it, it's a pain in the arse to get to and you don't have the time) anything up to a full week if clubbing
Paris. You've already been there, why are you going back? Why not fly home outta Madrid?

Minimum total = 72 + 13 days lost due to travelling = 85 days. And that would be hardcore mode, not relaxing holiday.

Basically, assume the fastest you can visit destinations is every 3.5 days.
Given you have 2.5 months, I reckon 4 destinations need to be chopped, not added.

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Where are you flying into and out of?

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we are taking a number of side trips from the bigger cities I was just naming the major places
With an average of 3 days per city, I don't quite see where you have time for side trips.

You really need to drop a few destinations to make this a more enjoyable itinerary that allows for some down-time and to create time to visit smaller towns.

I want to see everything!
I live in one of the smallest countries in Europe and haven't yet seen everything here, let alone in the rest of Europe. Accept that you can't see everything and take our advice at heart: less places, more time in each place is really the best way to see and experience a lot, unless you're a fan of train stations, motorways and airport lounges.

I guess your next question is which places we recommend you drop from your list; if you need our opinions on that, feel free to ask but please do tell us why you selected them in the first place.

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which places we recommend you drop from your list; if you need our opinions on that, feel free to ask

My advice would be somewhat different. If you don't yet have any informed opinions or preferences, I'd suggest researching until you do.

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The list you ask for would get endless.
Ancona isn't that bad. Good day trips from there to Frasassi caves, Assisi - Perugia, Gubbio, the Abbruzzi; possible 3day trip to Rome (Ancona dp 6.17 - Rome ar 9.40, dp 17.25 - Ancona ar 20.31) resp 2day trip to Florence (Ancona dp 6.10 - Florence ar 9.05, dp 19.30 - Ancona ar 22.40).

There is absolutely nothing to visit at Interlaken: it's just a local transport hub for journeys into the Jungfrau and Grimsel areas and to the Ballenberg Swiss Village Museum.

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BTW: as you have family at Ancona, you could aslo choose Ancona as a base and do from there
day trips to the surroundings (Marche, Umbria, Emilia-Romagna, etc.) may be during 1-2 weeks
a 3 day trip to Rome
a 3 day trip to Florence and surroundings
a 3 day trip to Termoli, Tremiti Islands and the Gargano
a 1 week trip to the Croatian coast (ferry to Split)
a 2 weeks trip to Greece (ferry to Patras)
etc. etc.