For feeding time, he has now made a mental association: go crazy, jump on my person = I get food, I get it even faster when I grab it myself.
There is a chain of behaviour and reward set up for him, and he truly believes with all his heart that his behaviour is what gets him the food. So the trick is, to give him a change of heart.
Now he will have to accidently find out that a different behaviour will get him the food, and he will want to hang on to his old behaviours, as that has worked for him so far. He will find out that what will work from now on, is to sit and wait quietly.
So at feeding time, be patient and wait him out. Ignore him, let him have a bit of a crazy time, stand there not reacting. Don't look at him. Don't acknowledge him, don't say a word, tune him out, draw your energy inwards. At first, he will get worse!
as he tries desperately to do what he thinks he is supposed to do. "Hey! HEY!!! LOOK at me!!! I'm doing it all!!! I'm doing the FEED ME dance!!! LOOK! Can't you see!!!"
Wait, wait, wait . . . (wear jeans and thick clothes so you can ignore his crazyness easier). At one point, he will stop to think about what is going on. the INSTANT he has stopped, is standing with four feet on the ground, be quick and put his food down. AHA! He did something different, and he got fed! His little brain just got a jolt.
Next time, he will have forgotten everything, and will be acting crazy again. Again, wait him out - this time, something in his brain will send a signal that his dance isn't working a bit sooner than last time. He will stop and think about it "Hey, how come my jumping on you isn't getting me the food?". Again, be calm, and quick to reward.
with repetition (two, three times a day?), the jumping will be shorter, the standing still will come faster. Then he has to stand still longer. One second, then he gets rewarded. Then two, three seconds. etc. If he breaks and starts grabbing, jumping again, go back to being a statue.
In about a week, if you are consistent, there should be a big difference in how your pup acts when the food bowl comes out. In a week of when he waits for you consistently, you can start asking for a sit (reward him right away after the sit). As you do training aside from the feedings, he will learn to sit stay. When you feel he is solid, have him sit and hold his sit as you get his food and bring it to him - but don't rush this part. Give him time to re-program his brain from "jumping around and snatching is what gets me the food" to "waiting without moving is what gets me the food".
As for the walks, if he isn't pulling on the leash, I would let him carry it, but that is personal preference. At this age, I'd just be happy that he WANTS to go on walks, and wants to carry something.
If he really likes to carry things, maybe he can carry a ball or toy on his walks? Then he won't be able to grab the leash.