From my understanding, you'd be able to make every charge capable of being delivered as a ranged touch attack. However, keep in mind that you'll be provoking attacks of opportunity each time. Also, I don't think you'd be able to deliver this multiple times per round unless you do so via a full attack with unarmed strikes (or weapon attacks if you have spellstrike). There's also the possibility that delivering the charge at range is only possible with the initial delivery, as part of casting the spell. Either way you need to be careful with this, since using it as a ranged touch attack would provoke an attack of opportunity on top of what you'd provoke by casting (and if you're allowed a full attack, on top of what unarmed strikes provoke, and once per ranged touch attack if you have multiple attacks from BAB). And you also need to keep in mind that holding onto the charge will keep you from being able to touch or be touched by your allies without hurting them, so you'll need to remember to dispell the charges you still have if you need to. To the best of my knowledge, though, the Str damage it incurs should stack, so being able to make multiple attacks per round is a good thing.
Yes.
The feat says it transforms the range of the effect to "Close," and serves as a Ranged Touch Attack if it was a Melee Touch Attack before. Ranged Attacks, including Ranged Touch Attacks, provoke an Attack of Opportunity for every attack you make within a threatened area.
The only other question that needs to be asked would be if transforming the effect from Melee to Ranged still allows you to hold the charge. Per the rules, you wouldn't be able to, and to which case, it wouldn't be worth it.
If I understood well , for each level of caster i can make one attack more in the same round With chill touch, so if i use with "reach spell" and im level 3 , that Allows me to make three ranged touch attacks at the same target or several?
The penalty of force builds upon the same target?
You are wrong. You get to make ONE attack as a free action after casting the spell. ONE. The ability to attack multiple times means that you're still "holding the charge" after you touch an enemy, but you still have to spend your regular actions to make those touch attacks.