Train travel in Italy

Check the cost of point-to-point tickets and compare to a railpass. Remember to add reservation fees for the trips on fast trains. Trenitalia.com will show prices up to 120 days ahead, with super-economy (no refunds or exchanges), economy (some changes possible for a fee), and base fare (full price, exchangeable and refundable within specific time frame). These fares are for first (higher) or second class.

Rail passes almost never pay off in Italy where fares are moderate. Your itinerary definitely doesn't involve long-enough trips to make a pass economically sensible.

You can easily check fares on the TrenItalia website. Except for any regional train you might take for part of the trips to and from Lake Como--those fares won't vary, you can save substantial money by buying tickets soon after they go on sale for your travel dates, but the cheapest tickets will be non-changeable/non-refundable and will restrict you to the specific date and time you choose, so do not buy until you are certain of your timing. And if you're planning a trip on your arrival day, wait to buy that ticket until you are Italy, since flights can be unpredictable.

You'll need to use Italian station names on the TrenItalia website:

Malpensa Aeroporto for the airport
Milano (Tutte le stazione) for the city
Venezia S. Lucia
Bologna (Tutte le Stazione)
and the specific town on Lake Como

Take a look at the same-day prices, then look at the prices for trips during the third week of July.

The difference is the savings from early purchase.

After you decide on hotels in Milano and Bologna you can determine which train station is best if your train makes multiple stops. (The fast ones often do not.)

The Trenitalia website mentioned above, works perfectly. Payment by credit card, an emailed pdf for printing at home (I always make two prints to be on the safe side). Never had any issues with them. The only thing to remember is using the Italian originals for station names.
On those long-distance trains 2nd class is comfortable enough.

Thanks everyone for the replies.

Venice question.

Is it better to do a cicchetti crawl tour or just go on your own.