Do NOT even consider/think to send (or tell) anything to USCIS about your marriage. Read it again-DO NOT. Applicants need to send only those supporting documents which are mentioned on the list provided by USCIS along with the naturalization application than anything else. Anything more than those documents could jepordize their situation. Even at the interview, NEVER EVER say anyting voluntarily to the officer. If USCIS would like to know/see something, they would either send REF (Request for Evidence) or would ask for an explaination at the time of interivew, and that's the only time applicants should provide documentary evidences or explaination.
Since each person is different and unique in this world then it goes to immigration officers too. Some officers are easier than others. Thus, it could be possible that the officer who would interview you might overlook this critical fact in your case and might not ask anything about your marriage. All I've said earlier is that since you got separated from your husband so shortly after obtaining your green card then your marriage most probably be seen as a sham marriage even though you have your story to say otherwise, like having dated him for 10 yrs prior to getting married and didn't marry him before when his family asked you...etc..etc...
That's why it's very important for you to collect as many evidences possible to prove the bonafide of your marriage. These documents should be more than what you provided when you requested to remove the condition on your temporarily green card. A lot of folks mistakenly believe that once a green card is granted then govt. cannot take it especially if someone would have it for many years. But these folks are wrong. Govt. can revoke a green card anytime they want. Having a green card is a privilege, and not a right. If govt. would suspect or come to know something material to fraud/lie then they can even revoke the citizenship even after 100 of years later...
And many people also mistakenly believe that at the time of naturalization USCIS cares about the applicant's life only since s/he became a Permanent Resident which is not true at all because naturalization relief is different than any other immigration relief. By applying for naturalization, applicants put themselves to get scrutnized by US govt. I don't have time to mention about thousands of cases wherein USCIS revoked the Permanent Residency when those immigrants filed for naturalization because govt. found something which they called-fraud/lie to US govt. at the time of obtaining green card or at the time of obtaining any kind of nonimmigrant visa at US embassies/consulates. Just because someone had no problem at the time of obtaining green card, that doesn't mean s/he won't have any problem at the time of naturalization. Similarily, just because someone had no problem in removing the condition on their temparory green card or in becoming naturalized citizen then that doesn't mean that every applicant wouldn't have the problem. You won't get the same officer who approved your green card application or the same officer who approved other people's case without a question. Thus, you should always prepare yourself for all kinds of situations based upon your own situation than others.
As for you asking if you could remain married for the sole purpose of being naturalized then I don't give my opinion on how to circumvent immigration laws for a selfish reason but if you gon't get divorce until Oath would be taken AND don't tell ANYTHING to USCIS about your separation and shaky marriage AND would collect documents to prove that you and your husband are happily living together then you don't have any problem in getting naturalized under 3 yrs rule. But the key point is-you must need to have enough documents to prove that you and your husband are happily living together like having same address on both of yours driving license, jointly filed taxes, joinly owned house or lease in both names, joint bank account, alot of pictures together, and etc...Must be current documents though if you want to file N-400 under 3-yrs rule...
Who is paying to the house or who bought it, is totally irrelevant here. Also, having dated your husband for 10 yrs prior to being married is also irrelevant because many people date multiple people at the same time but get married only later on just for a selfish reason. As for being nervous, then you don't need to get nervous. USCIS normally asks just general questions about marriage at the time of Naturalization. Pretty much they just ask for documents. If you get nervous then they would suspect more. Bringing your husband to naturalization interview or having an affidavit from him about the bonafide of your marriage is meant nothing to USCIS. Otherwise there won't be a need for an interview for a green card based upon marriage to a US citizen.
Good luck...
I guess it is the wedding cake. Count yourself lucky if you keep your permanent residency and don't have problems naturalizing in the future. Hey, I'm kind of kidding, but it is possible that at time of naturalization the officer will ask you questions about your marriage and divorce. I think you'll have to wait at least until you have your Green Card for 5 years. I think Johnny Cash has given you correct information.