kes me nervous that reviews are over 6 months old.
There can be many reasons why a sitter may not have any recent reviews, including the fact that his/her customers are repeat ones and only might have reviewed once. Also, many customers either might not take the time to actually write a review and only give the sitter a star rating, so you won't be able to tell. I have a repeat customer who has never reviewed me, and I don't bug them about it. So there's really no need to be nervous about the lack of recent reviews.
During the past couple years, the overall need for sitters has been drastically reduced, because a lot of people have been caring for their own pets while staying home, including those who worked from home and those who didn’t travel.
It’s not necessary to fill in the dates, but by doing so it will exclude sitters who are not available during the dates you need. You can contact the sitter about a service and engage in a conversation through rover messages or their rover number. If they seem like the right fit, arrange for a meet and greet to introduce the sitter to your pets.