Yes. Penalty dice from wounds do reduce your stats for the purposes of help (and FORKing) thresholds.
Helping dice are based on the exponent of your ability. BWG p. 36 (my emphasis throughout):
If the exponent of the helping ability is 4 or lower, one die is given to the acting player as help. If the exponent of the ability is 5 or higher, two dice are granted.
Wound penalties reduce the dice you roll. BWG p. 488:
Wound penalty dice are subtracted from stats, skills, Reflexes and Steel. Health, mortal wound, Circles, Resources and Emotional Attributes like Faith are not affected. Do not refactor attributes or damage due to wounded stats. (Note that Reflexes is affected directly.)
The number of dice you roll when you actually use the ability is the "exponent." BWG p. 12:
The number next to your character's stats, attributes, and skills indicates how many dice to roll when that ability is called upon. We here at Burning Wheel HQ call that number the exponent of the ability because it is representative of the character's actual ability in that area...
Therefore, wound dice reduce your effective exponent, which reduces the value of helping dice you grant.
FORKs are defined similarly to helping dice (see BWG p. 36), so wound penalties will also reduce the value of FORKs.