My wife has vulvar vestibulitus, whch causes extreme pain during intercourse. I know that generally ejaculation should only occur during intercourse. Given that this is too painful for my wife, would there be a justification for being intimate with each other to the point of ejaculation apart from intercourse? This is in no way to avoid pregnancy. We are very open to conception, although conception is not a likelihood for us for a number of reasons apart from the obvious.
I am unfamiliar with the condition, and sincerely hope that there is a medical solution for her problem.
Regarding the morality of sexual acts between married couples, the answer to your question is that orgasm outside of a completed act of intercourse is a sin against the Sixth Commandment. So, no, you could not do what you are proposing.
My personal opinion is that since you and your wife are entitled to consensual sex and medical conditions make the only Church approved method impractical, you would be well within your rights as a married couple to pursue other options.
As I hinted at earlier however, the Church has only one approved method.
Oh, and I would like to see how sex with one’s spouse could possibly be said to be adultery, even if the method of intercourse is seen as sinful
What you are proposing is an intrinsically evil act that is always gravely immoral, regardless of intention or circumstances. Do not read the books suggested in the post above. Instead, read the documents of the Magisterium on the subject of sexual relations and morality:
The Church, nevertheless, in urging men to the observance of the precepts of the natural law, which it interprets by its constant doctrine, teaches that each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life.
Union and Procreation
This particular doctrine, often expounded by the magisterium of the Church, is based on the inseparable connection, established by God, which man on his own initiative may not break, between the unitive significance and the procreative significance which are both inherent to the marriage act.
The reason is that the fundamental nature of the marriage act, while uniting husband and wife in the closest intimacy, also renders them capable of generating new life—and this as a result of laws written into the actual nature of man and of woman. And if each of these essential qualities, the unitive and the procreative, is preserved, the use of marriage fully retains its sense of true mutual love and its ordination to the supreme responsibility of parenthood to which man is called.