His Will is really 15, he just gets an extra 3 from Templar armor, and 1+ from Runic Token. Magic really 12, and Con is really 17. For Magic and Con, I think the boost come from his Templar spec iirc
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Also whats the diffrence between using a say health potions at Self: Health < 50% and Self: Health > 50%???? That s*** is mad confusing lmao
The tactic system is a little confusing at first, but it is pretty powerful when you get the hang of it. At least for some tasks.
The best way to think of it is a series of If-Then statements where you pick a condition, and then pick an action. The numbers are priority, so number 1 has highest priority. The game will check them in sequence and if the condition is met, and the action can occur (talent not on cooldown, enough mana / stamina, etc), it will perform the action. Once it performs an action, it goes back to the top.
So for health pots, you want to use a < whatever number. That way when he is at high or full health he doesn't try to use a pot, but if it drops then he will.
Generally you put sustains like Shield Wall at the top if you want them to be run all the time. Threaten also can go up there, although it isn't hugely efficient until Alistair can output some damage.
Next you can put the actives. The first job Alistair has is to stay alive. That means healing with pots should be at the top of this section, unless you want to always manually control them (I do not for the tank). Next I go with Taunts, and then CC. Since damage dealing helps grab aggro, you try to fit in a generic attack order near the bottom.
So a basic tactic set for him that should work ok would be something like this:
Self: Any ---- Activate Shield Wall
Self: Health < 50% ---- Use Lesser Health Poultice / Health Poultice Least Powerful* whatever
Self: Surrounded by 3 enemies --- Taunt
Enemy: Attacking Morrigan --- Shield Bash
Enemy: Attacking Wynne --- Shield Bash
Enemy: Nearest Visible --- Attack
*I have the Advanced Tactics mod which changes a few things in tactics, and I don't quite remember the exact options for poultices in base game. With the mod it is "Health Poultice: Least Powerful" or you can go most powerful, and it will pick out of what is available.
I actually don't typically run lines like the Shield Bash ones for my tactics, because I would do that manually. So I might have
Enemy: Nearest Visible / Health < 75% --- Shield Pummel
Thrown in there somewhere. Just depends on what you want the AI to be able to do on their own. The most important things though are the health pots and taunt. You want him to Taunt as much as possible to keep the heat off other units.
Threaten increases the aggro generated by damage, but if Alistair isn't doing much damage at all it is questionable. You can add a tactic Self: Any --- Activate Threaten near the top if your Alistair isn't running out of stamina for Taunts and the occasional Bash.
There are some decent resources for tactics floating around. Hate to say "do a search," as my brief one didn't turn up one I was remembering. I will look later, but maybe you will find it before me. 
As far as points go, you will need some more Str to allow Alistair to wear heavier armor. Needs to get to 39 eventually. The sooner the better really because that will allow his armor rating to go way up. Since you will not be taking Templar on the Warden, that means you can give Knight Commander Plate to Alistair if you can get the ~23 gold together.
Since he is WnS, you need to get at least 26 Dex, but the more the merrier so he can avoid damage. Keep in mind that the 1 handed swords, axes, and maces only gain damage via Strength. So it might be worthwhile to give him a dagger as dainbramage said. Half the time I don't even worry about it since he is the only WnS warrior and he gets whatever the best 1H weapon I have looted (since the best daggers go to Leliana or me most of the time in my runs).
I have also made him a dual dagger "tank" with sky-high dex which was pretty amusing. His armor rating was a bit wimpy on that run though, so I wouldn't recommend it the first few times through the game.
edit: If you are using a Healer (which is what Wynne basically starts as), it is helpful if they have a health pot listed for themselves near the top of their tactics, then the next couple devoted to tank healing.
So for Wynne:
Self: Health < 25 --- Use Health Poultice Least Powerful
Allistair: Health < 50 --- Heal
Allistair: Health < 75 --- Regeneration
Ally: Health < 25 --- Heal
Something like that. Might not want to have her heal set at the same level as Alistair's health pot level, but I don't remember the gradations in base game tactics. In Advanced Tactics you can pick by 10's. Depending on how many lyrium pots you have, that might need to go in there somewhere. Also debatable whether Group Heal should go on there.