I'd agree in a way with newt and — You shouldn't worry too much about hackers. I'm not saying you shouldn't secure your app at all, but just don't freak out. If you want to secure it completely, this will be a neverending fight as they will find a new way for your new securities all the time. If you both (hacker and you) get stubborn enough this will be a ping-pong game between you both.
So I suggest to secure it from the noobies-hackers and kids with some cracking soft and that's it. They are the majority of problems. Real hackers which dive into your code and search the way to bypass your security are really minority. And well if they struggled to do it... take it as a complement, it means your game was worth a hassle.
From my experience, the noobies-hackers are less than 0.5% of your game users. In my case it was 0.2%. The real hackers are far less part of your game community.
Now keep in mind that most of the noobies-hackers have no idea about anything related to development. Someone showed them a tool and they simply use it. So if you want to get rid of kids who make direct changes in your storage, simply encrypt the data - this step should already discourage most of kids.
For data encryption you have to use some two way hashing algorythm like Base64. So you could encrypt and decrypt data. Also don't bother to encrypt/decrypt all the values separately. You can use one LocalStorage key "gameData" and save there encrypted Dictionary JSON which you can then load and decrypt on game start. In that way "hacker" will see only one local storage entry containing some mystery hash and you will have your data loaded in RAM memory.
You can go a bit further and give some salt to the encryption process in case there is one smarter kid who heared of Base64.
Much more secure would be to have all data on your server in some database and sync this data each time user spend resources. But this is pretty complex to do for someone who is not experienced in PHP/MySQL or any other backend technology as you have to secure your data transfer as well. If you have time, then go learn it, backend technology is very useful and fun, if not then encrypting storage should do the job for kid-ackers.