anyway to tell in advance how much train reservations will be?

Go to www.seat61.com for all of your questions. Most avoid Eurail passes since they usually don't save any money and can be a real pain. Point to point tickets on Trenatalia, bought 120 days prior to travel and other country's train systems are the best bet. Do some research and you will be much happier.... and less stressed.

Clearly, you are doing research, so I am unsure about the previous comment.

There are no reservations between Lauterbrunnen and Basel. First class reservations on the TGV from Basel to Paris run $80. I don't know about 2nd class.
The other concern with the rail pass is that you really should make those reservations as close to 90 days in advance as you can because there are limited number of seats allowed for rail pass tickets on this train. You could have a rail pass and still end up needing to buy a ticket.

Often the value of a rail pass isn't always that it saves you money. It might not. The person who a rail pass is a good fit for is someone who would like to have a great deal of flexibility in their plans.

To answer your question, Rome to Cinque Terra can be done with an IC train to La Spezia, $4 pp res fee.
CT to Florence can be done with regional trains with no res fees. Florence to Venice and Venice to Lauterbrunnen will require Freccia trains with a $12 pp res fee. Lauterbrunnen to Paris will be subject to passholder limitations (only a set number of passholders allowed on the train).

To give you a quick cost estimate overall, just plug in each of your locations into www.rome2rio.com. Look in the left column, and you can see the approximate cost for a train ticket (or bus ticket) for that leg of your trip.

We were in Switzerland for several days last year, and it was still cheaper for us to skip the Swiss card options and just purchase individual tickets.

Visit www.eurail.com/plan-your-trip and it will take you step by step and show actual fees if you need reservations (you don't always need them). Reservations can be very cheap- and many routes don't require them. We travel through Europe most months of the year and find Eurail passes to be very convenient. It isn't all about saving money but about convenience too. If you go the link, you can buy passes, choose trains, and make reservations all in one session at one time and have it done and travel without worries. They are in no way a pain, do help save money, take the stress out of travel, and free you to choose to go to other countries if the occasion arises. Most people do not avoid them. They are hugely popular with travelers. Even in France, you can make reservations when buying your Eurail pass and not worry about limitations for passholders since your place will be reserved.

You have four train rides within Italy and will probably use a fast train on each one of them, so that is €10 euros or $12 x 4. Italian seat reservation fees are described on our Italy rail pass page. No deadline to book those, although a particular train or class could fill up by the time of departure.

TGV reservations departing from Basel are more expensive, $40 per person in 2nd class, but TGV reservations departing Strasbourg are usually only $11. Limited places are available for pass holders, so those should be booked at the same time that you buy the pass.

Your connections within Switzerland don't need reservations, nor do any regional train connection in Italy.