If the reason domestic partnership was not possible is related to geography, employment or residency, then these barriers will not prevent you from marrying. You may, however, need to travel to another state to marry and your home state may not recognize that marriage.
That depends on the reason why domestic partnership was denied. Many requirements for domestic partnership do not apply to legal marriage; for example, you must live together to register as domestic partners, but you are not required to live with your legal spouse. Some domestic partnership registries require that you be a government employee whereas there is no such requirement for marriage.