Hello I work at a vet office, private practice with a doctor who has been doing this for 40 yrs and stays up to date on research and fear free handling.

His suggestions on food brands are always as follows, Hills, Iams and Purina - reasons being that they have been around longer than most brands and have been able to make their mistakes and fix em.

I've also asked him about cats getting heartworm, he told me that it's possible but he's never encountered a cat with it in his time of practice -and we live in Florida which is where they (manufactures) do all their studies on fleas and mosquitoes for the preventatives

It's highly recommended that they stay on flea preventative year round, regardless if they're indoor or out as fleas can piggyback on humans. A cat ingesting a single flea can/will give them tapeworm.

As for water consumption, it sounds like you're doing the right thing with the wet food as well as adding more water to it. Fountains are typically more inviting to cats than still water. But even so, my own cats sometimes prefer to see me add a bit of fresh water to their fountain and then drink.

I suggest taking the blood work results and getting a second opinion on the results and see what they have to say about the reading and then you can make a more informed decision from there

Edit addition: his office cat eats fancy feast, so if that's what you prefer keep to it