Yes, if you are living apart from your spouse the interview is likely to be tougher and you'll need to explain the separation (preferably with evidence, like bus/airline tickets and phone bills showing you're calling each other frequently).
However, don't bother with OPT. Given that you are married to a USC, once you file the I-130 and I-485 (the main forms for your GC application), you are allowed to stay in the US legally until your GC is granted or rejected. Filing I-765 along with the I-485 will allow you to get an employment authorization card, and this GC-associated employment card will be better than an OPT employment card, because the GC-related one is not restricted to your field of study. And the GC-related employment card doesn't obligate you to work, like the OPT employment card would.
But don't leave the US until you've applied for the GC and obtained Advance Parole, because you could be refused entry with an F1 visa due to having immigrant intent (made apparent by your marriage to a US citizen).