I think I'll try lay this out on my opinion on the matter.
30 Yard Screams - All I can suggest, on opposition instructions you close down opposition players with high long shots (Even if it's low, look at their technique as well), also show them onto weaker foot. If wingers look to cut in and shoot, show them onto their outside foot, so they can't cut in and shoot. Plus, maybe it's your goalkeeper.
'Walking' it in the net - Your players obviously arn't getting close to the opposition striker, maybe set your defenders marking to man marking. This way they keep close to the opposition strikers, which means when they get the ball they wont have much room. Obviously man marking and zonal marking have their flaws, so maybe one central defender man marks (I'd make sure they man mark the strong striker) and the other zonal marks. Could work for you. Oh one more thing, your full backs should also be on man-mark, I find it a neccesity. Also, with your 4-4-2. Make sure you have a defensive minded midfielder, rare forward runs, closing down should be a high and hold up ball to retain possesion (Must have high strength).
Missing really easy chances - Well, if this is like 6 yards out (Robbie Keane at Liverpool). Use the right motivation techniques, keep morale high. Although I would look at your strikers Finishing, Composure, Concentration and Technique.
Taking stupid long shots - Obviously this will have to do with the players mentality. When the striker receives the ball, how far/close is the other attacking players to him? Your player probably has no one near him, and with this high mentality, he just shoots. So I'd try a number of things, lower the players mentality and put the strikers passing at mixed, then you can tweak the passing to the range of where the other team members will be. So when your striker receives the ball, pause the game and take a look. You'll figure it out.
Strikers not taking time - Obviously linked to above. But, if they have plenty of space, tick 'Hold up ball' and 'Run with ball' often. So then they can wait for their team mates to catch up and then the striker can get them involved in the attack.
Tactics - You said you've tried a variety of tactics. Here is my advise, stick to one tactic from now on and just tweak it. Read up on FM Base's Tactical Theorems on the Download Pages.
Players useless? - Maybe, just try and improve the squad as you go along. Get your tactics right first.
Hope i've helped.