hi,
glad to hear you have rescued a dog, thats great.

Food:
when you eat, whether it is on the sofa in front of the tele or sat round a table, you should always tell him no if he comes near, tell him leave it or go away and dont look at him just ignore him. he will soon get the idea that he is not going to get anything and will lay down and possibly go to sleep. my pup does this already and shes only 9 weeks old.
you should never give your dog food off of your plate and never give them titbits as they will then expect them when you eat and they then may not eat their own food, because they think they will get your food if they wait long enough.

Tireing him out:
all dogs need mental stimulation as well as physical stimulation. there are a number of things that you can try, one of them is to get him fitted with a dog backpack, so when he goes out for walks he can wear it and it wil;l drain twice as much energy than the normal walk. you should get him vet checked first to make sure he doesnt have any back problems and to get him weighed as he can only carry 10% of his body weight maximum. this is a great energy draining method and works straight away, you will see the results and will be more than happy with them.
once you have the all clear from your vet, you can then measure him up and buy a backpack either online or from major pet stores. they cost around £30 depending on where you get them, but they are well worth the money.

hope this helps, if you need any more info then please message me and i will try to help as much as i can.