S. R. Faruqi:

chālāk = swift-moving, masterful, intelligent

The word chālāk , Sauda too has versified well:

taṛp apne dil-e be-tāb kī ḳhāt̤ir ai shoḳh
barq se lī hai tire ġhamzah-e chālāk ke mol

['agitation', for the sake of its own restless heart, oh mischievous one,
has bought with/from lightning your adroit sidelong-glance]

But because there's no proof that passion has the authority to buy the adroit sidelong-glance, the expression in the verse remains incomplete; only the excellence of ġhamzah-e chālāk remains intact.

By contrast, in Mir's verse is complete in every way, and in it both meanings of chālāk have been used with great excellence. The rip in the collar has become longer and longer until it has reached the garment-hem, but even now I have hope that my swift-moving hands, or my intelligent and skilful hands, will come up with some way to continue the ripping further.

It's a fine mirroring of the innocence of madness-- that the madman is capable and intelligent, but his thought is not logical. He knows that his hands move very swiftly, and are masterful at collar-tearing; for this reason he hopes that somehow some kind of additional tearing can be done. So what if the rip has reached to the garment-hem-- his adroit hands will work out something!

In the construction kaf-e chālāk an additional excellence is that the person who is a master at working with his hands, or knows well how to use his hands, is called chālāk-dast .

FWP:

SETS
MOTIFS == CHAK-E GAREBAN
NAMES
TERMS

What is the object of the speaker's 'expectant/hopeful' feeling? SRF says it's for his dextrous hands to manage to continue the ripping even further. (Perhaps inward, to his heart and liver.) Or else he could be hoping that the beloved might, even now, be moved by his mad plight and give him at least a small shred of her attention.

For surely one purpose of this dramatic garment-rending show of madness was to attract her notice? Might she not enjoy the spectacle of such an extravagant, maximal display-- a crazed lover who doesn't just rip open his collar, but goes right on ripping down to the hem of his garment, and doesn't want to stop even then?