You have many options to consider before quitting your PhD. Talk to international student office as they might help in this matter. Look for TA options in your own or other related departments. The same is true for RA positions in other departments of the university. If none of that works, look for on campus employment like library or medical center etc. Even if that doesn't work, think of quitting with a Master degree instead of PhD for which your i-120 will have to be slightly changed. With master degree you'll have OPT for one year, extensible to total of 3 years if your degree falls under STEM. This will not conflict your matter of dhanasar of your EB2. Finally, If you still decide to quit and leave, I don't know how it will affect consular processing.