I would assume the wait command would work like the others, with a number attached to indicate how long to wait. Once you need it to wait longer than a few seconds, you might as well wait to draw it.
I got nothing for looping instructions though. You may not be able to, since you're usually drawing quite a few chalklings. For example, if you want to breach a double circle defense, a looped program could let you send a chalkling to attack, then keep moving forward to attack the inner circle; you'd loop the 'move forward, attack'. However, since you'd have several chalklings attacking at once, you probably wouldn't need/even be able to do that; you would just tell them to move forward until they hit chalk, so the ones behind would just move through the gap.
And all of that might not matter, as the chalkling may just remember the last one or two commands anyway. On the binding chalklings page, it implies they remember instructions in the bit on using too long a line to connect them to the circle, saying they can get distracted. So once they're through the first circle, or defeat an enemy chalkling, they may just go looking for more to attack.
As for your last question, I think it wouldn't work. Intent is huge with rithmatics, so unless the drawer intends for the chalkling to begin, I think nothing would happen. You'd have to start over.