It is a busy trip. I have been to nearly all the places you plan to see (all except Minsk and Finland).
I suggest while in Brussels spend a day going to Brugges, which is not that far from Brussels. Otherwise, skip Brussels entirely.
You have significant travel between some of your cities. Lisbon and Portugal are great places to visit, but travel from Lisbon to Seville may not be so easy. A few years ago, I explored this and found the rail connections to be very poor. Your might consider saving Portugal for another trip, when you can do Porto and the Douro River Valley.
Seville is wonderful and deserved a 3 day minimum. You might start in Seville and spend four days there and four in Barcelona. Add another day to Paris.
Also, we loved Lyon, France and Provence, but you might skip Lyon, since you won't have time to visit Provence and the South of France that much. Instead consider taking the high speed train from Barcelona directly to Paris.
While in Luxembourg, try to visit the city of Viaden, it is worth half a day.
With 11 days in the UK, clearly London deserves some time. Consider some day trips to Canterbury, Cambridge, Winchester, Oxford, Stonehenge/Salisbury or Bath. You won't have time for all. I forgot, if you love Shakespeare, then Stratford Upon Avon is a must.
Berlin and Munich deserve more than 3 days each. I haven't been to Minsk, but my Son has been there and enjoyed it, but it is a bit out of your way. Consider spending your Minsk time in Berlin and Munich. Also, from Munich most people take a trip down to Garmisch and Fussen to see castles or go up on the Zugspitze (highest mountain in Germany).
It will be Winter and going to northern Europe, you may encounter snow.
We did the Baltic States on a guided tour after doing Russia and loved them all. Plan on two days for each country minimum.
You will be close to St. Petersburg, Russia. You could spend several days there. I know you don't plan to visit Russia. It does require a visa, but the city is amazing.
Take care while traveling alone. Be sure to avoid some of the seeder places in inner cities at night. Europe is relatively safe, but there are places that require caution or to be avoided altogether.
Pickpocketing is a huge threat in places like Barcelona and Paris, so take precautions. I wear a money belt in those cities.