I think eurail could make sense, especially if you want to keep some flexibility in the second half of your trip. But you have to calculate additional reservation costs in France and Italy. These reservation costs can be cut down if you don’t mind longer travel times or more changes of trains
Paris - Bruges - Paris: I suggest travelling via Lille and Kortrijk. You only need a reservation from Paris to Lille and vice versa, which costs 10€ p.P and train when booked in advance, otherwise 20€ until the train is full.
Paris - Zurich: the direct TGV Lyria has a 29€ passholder reservation fare. To save money, I suggest to travel via Strasbourg or Mulhouse and take regional trains across the boarder. The TGV then has the same fares as above.
Switzerland is one of the best countries for passholder as the train fares are really expensive, the trains frequent and without any reservations. Simply use your pass as a ticket and go.
Zurich to Milan can also be done reservation free with an easy change in Lugano.
In Italy, high speed trains have a 13€ passholder fare but it isn’t necessary to book far in advance because trains are frequent.
To see the availability and to book passholder reservations for all your trains, use www.raileurope.com (desktop version). For planning, use e.g. bahn.de or the DB Navigator app (more reliable than the railplanner app).
IMO a 10 day pass should be enough for your plans because you can take as many trains you want on a travel day and public transport in the cities isn’t included in your eurail pass.
Advanced fares for direct high speed trains from Paris to Belgium and Switzerland might be only a little bit more expensive than the pass fare if you want to save a travel day.
