Again, I don't have my PHB in front of me right now, but my recollection is that you can keep re-summoning your pact weapon all day long if you really want to. Each time you do, it disappears from wherever it was and appears in your hand.What do you mean by "You can do it every round if you feel like it. Don't know why you would, though."? Do you mean dismiss it?
Bladelocks are a really interesting subclass. I spent some time tinkering with them last night and again this morning. A dip in fighter before starting warlock looks very helpful, mainly for the fighting style, but also to get you proficiency with martial weapons (if you're dual wielding--auto proficiency with your pact weapon doesn't help with your off-hand weapon) or heavy armor and shields (if you're sword-and-boarding or fighting with a great weapon). If you want to go straight warlock, then either Two-Weapon Fighting or Moderately Armored/Heavily Armored are must-have feats. If you want to make a "dark paladin" type, bladelock with a dash of fighter seems like the way to go.