Since the weed is only brown but still attached it cannot be considered a loose impediment. However, one must also remember that a player may only "fairly" take his stance and must take, "the least intrusive course of action which results in the minimum improvement in the position or lie of the ball". If the action you described would improve the lie of your ball then you would be subject to penalty under Rule 13-2.

From a cart path, drop the ball within one club-length of nearest point of relief, no penalty.

From a water or lateral water hazard, drop a ball within two club-lengths of the point where the ball last crossed the margin of the hazard, adding a penalty stroke.

From an unplayable lie, drop a ball within two club-lengths of the spot where the ball lay, and add a penalty of one stroke.

The spot of nearest relief is determined by the ball's location. See definition of “nearest point of relief” on page 11 of Rule booklet.

There is no Rule that would restrict a player from carrying both right and left hand clubs in their bag. Rule 4 does limit the player to starting the stipulated round with not more than 14 clubs.

I would not consider your actions as building a stance. However, by using your feet be careful not to move anything that is embedded, such as rocks. Also be aware that this action is not permissible in a bunker or water hazard. Under these circumstances, a favorite expression of mine comes to mind, “avoid the appearance of evil”.

No. The general rule of thumb would be that, should a player create irregularities in the bunker prior to playing from that bunker, the player would have to deal with those footprints. Should the player repair any damage prior to playing he would be subject to penalty under Rule 13.

Unfortunately you incurred a two-stroke penalty for playing from a wrong place (see Rule 20-7). The good news is that it is not considered a serious breach that could end up with a disqualification penalty if not corrected.