Link's projectiles are by far some of the slowest moves in the game, as far as startup goes. Pulling a bomb is slow, blowing it up is slow, the boomerang is telegraphed, the arrow is almost useless in neutral, etc etc etc. Judging by your statement that your friend likes to dash attack behind projectiles, I can tell that he's probably only a mid-level link, which means your frustration should be easily curable.
Hi, I'm called "Who?" and go by the tag ~?~ online, and I'm one of the higher ranked Links as far as GSP goes and almost solo main him at this point.
I'm going to be bluntly honest about your thread here. No one can help you with your Link issue without really understanding your preferred to play characters AND how you perform in both neutral and disadvantage state. I know it sucks to hear this from someone, but you wont get help here. The only way you'll learn the matchup is to play it, and adapt, and discover tech that throws off the opponent's typical neutral strategies. i can of course play friendlies matches with you and teach you how to fight a Link by playing with you, but I'm not a campy Link like your friend here, I'll actually bomb juggle you on the ground with downthrow bomb fast fall first hit backairs until you're at 80+ percent. So don't expect the same stuff you might see from your friend. None the less, I would be glad to help you understand Link at a high level because I'm actually a pretty high level Link main. Just send me a private message if you want the practice.
IMPORTANT EDIT: I just noticed that you main Ike. HUGE tip. Use your neutral air on his boomerang and then approach. The end lag on Ikes Nair is pretty low so it's a very safe disjointed attack to counter the boomerang with.