Which service would you recommend from Venice to Orvieto on Monday 7th May & which stations are on the route?

Thank you for your email. From Venice>Orvieto, you will be changing trains in Florence. This will be a high speed train from Venice>Florence, and then a regional train from Florence>Orvieto. On the regional train, this train will stop in Figline Valdarno, Montevarchi-Terranu, Arezzo, Castiglion Fiorentin, Terontola-Cortona, and Chiusi. You can stop and get off the regional train in any of these towns, and then using the same ticket, you can get back on a later train to continue the trip. As to our recommendations, I really can't give you a specific recommendation as to which towns you would want to get off and see, because it would depend on what you want to see and/or do.
Because the train from Venice>Florence is the Eurostar Italia, if you get off the train in Padova, Ferrara, or Bologna, you will lose the remainder of that ticket, and will have to purchase a new ticket locally to continue on to Florence.
Please let us know if there is anything else we can assist you with.