Should I buy France-Italy Saver Pass(Eur225 - 1st class)

First of all, if you are younger than 25 years old, you may consider buying 2nd class pass as the seats of 2nd class is also comfortable and cheaper.
I believe you check the price in the website http://www.raileurope.com/us/rail/fares_schedules/index.htm. It is not the official site of French (SNCF) or Italian (Trenitalia) Railway. I am not sure whether they will have service charges. But I believe you should check the price of ticket from the official website:
Italy: http://www.trenitalia.com/en/orari_biglietti/index.html
France: http://www.voyages-sncf.com/dynamic/_SvHomePage?_DLG=SvHomePage&_CMD=cmdHomepageUK&WB=HP
You can get the most updated price from the above site. It's ture that you cannot find the price from Venice to Nice. So you can use US$171.00 = Euro 127.00 as a reference cost.
If the railpass is Euro 225.00, plus all reservation charges, it will be around Euro 310.00. If you are not insist in travelling on 1st class and buying railpass, you can buy tickets separately when you arrive Italy and France. You can travel on 2nd class. The cost must be lower than Euro 310.00.
If you prefer to buy railpass, please do not make any reservation in Hong Kong. As you may change your travel plan, if all reservation is made, you can change nothing !!! You can reserve the journey after arriving Italy. Except the journey from Venice to Nice (it should be reserved once after you arrive Rome), there will be many trains runs bewteen cities. For example, from Rome to Florence, trains runs every hour...
Hope i can help you.

yes, rite