1. Is it safe to travel to Croatia?
Even through the time of war, there were no incidents in the area of Novi Vinodolski or near. Now all burning issues are solved and there is no foreseeable danger. Fighting in Kosovo does not involve Croatia militarily nor (directly) politically.
2. Is it safe to come with the car?
It is reasonably safe, although all necessary precautions should be taken as usually. There is no car theft plague in Croatia. Roads are not in mint condition though, especially going south Adriatic. There is a chance for fine sport motoring if road is not crowded, but make sure you get good rest every now and than. Serious.
3. What kind of fruit and vegetables are available?
You can count on all kinds of f&v, as local growers offer their food on market. Prices are a bit higher than in larger urban areas due to the lack of competition, but they are reasonable. It is hard for me to sample because they vary, but $1/kg of watermelon and between $1-$3 / kg for common seasonal f&v is an estimate.
4. Can I make my own food?
I suggest bringing own barbecue (grill) and roast fresh fish ('plavica' at $2.5) or meat ($7). Barbecue has to be of the closed type as open fire is prohibited due to forest fire precautions. I suggest bringing your own food if you are budget oriented to avoid frustration. Milk is more that $1/lit and bread is around $1. Prices in restaurants are not over inflated. Some budget sample would point to $2 sardines, $4 pizza, $4 calamari etc. Larger sample soon.
There are no problems that surface as such. There may be restriction on import of fresh meat due to health regulations. Make sure papers for all people, vehicles and pets are fine.
6. Is swimming nude at pool or sea OK?
Pre and post season see a lot of nude bathing. Also at dawn and dusk, it is common to see nude swimmers. However, when the beach is crowded, there may mount peer pressure. Topless and small kid nudity is OK at all times. There is unofficial dedicated area for fkk enthusiasts though.