A wet is a reduced charge but is still counted as a prior if you pick up a new DUI in 10 years. A wet will help in many areas and has reduced fees and fines. If you want a wet and you should get an attorney.
I agree with Mr. Kaman. A Marsden hearing is your only recourse. The issue is judges very rarely grant them and you will be back where you were with the PD you do not like. Invest your money in a private attorney.
The arrest record will always be on your record. You record will show a case was dismissed. There is no way after you enter into this deal to successfully petition for factual innocence (and if is unlikely that you would be granted this even of you do not take this offer). Employers in California can only ask about convictions. You can honestly answer that you were never convicted. Now as for applying to a government job or licensing board you will need to disclose and explain the situation and...
I am not sure how this is a criminal question. Like it or not most of the recent technology that we all use today is due to the porn industry. It is one of the largest money makers on the internet and generates billions of dollars. So I would say yes people legally pay for memberships to porn sights all the time.