Can tummy tuck help IC symptoms?

I am not aware of any benefit of abdominoplasty for IC. The abdominoplasty will repair the space (diastasis) between your rectus muscles. Certainly there are cosmetic benefits as well but no known impact on IC

Severe cases of IC are debilitating and if you are experiencing
this, our deepest sympathies are with you. Abdominoplasty can do many things. It
can enhance the waist line, achieve a thin, tight, flat abdomen and
dramatically improve the posture and help lower back pain. Regrettably it doesn’t seem to be helpful for IC.

The benefits of a tummy tuck are extra-abdominal not intra-abdominal. It is theoretically possible that if one has a large lower pannus that the weight and overhang on the lower abdomen could potentially have some impact on the bladder/urethra. But this is more of an outflow issue not an internal inflammatory effect.

I am sorry to hear about the problems you are experiencing with interstitial cystitis. Unfortunately, tummy tuck surgery will not be helpful when it comes to controlling/decreasing symptoms.  Most patients who undergo  tummy tuck surgery do so after pregnancies and/or weight gain/loss; they benefit from re approximation of the abdominal wall muscles  as well as from excision of the excess skin/adipose tissue.  
Generally speaking, the “ideal” patient for tummy tuck surgery is one who has completed pregnancies, is medically/psycho socially/emotionally/financially stable,  has an excellent social support system surrounding him/her,  does not smoke, is capable of arranging enough recovery time and who has reached a long-term stable weight.  Best wishes.