Bismihi ta'ala
Islam encourages healthy sexual relations between husband and wife, and to cater for each other's sexual needs and lusts, as long as they are within the shar'i and moral boundaries.
It is highly mustahab to address their sexual needs. For example, foreplay is highly recomended, where first it is recommended to engage in mudāʿabah, which means verbal foreplay, then mulāʿabah, physical foreplay, and then mujāmaʿah, which is having sex.
Oral sex is a part of mulāʿabah, and there is no problem with that as well. In regards to semen, in Shi'i fiqh, it is considered najis, and therefore, should the husband ejaculate in wife's mouth, she must not swallow any of it, and must wash her mouth.
Also, the wife does not need to perform ghusl in this instance.
Of course, there are certain sexual practices in today's Western society that are inhumane, immoral, degrading and humiliating, but happily accepted by some. As Muslims, we we must not imitate whatever is out there, or what is in pornography, etc.
As much as our religion encourages intimacy and sex within marriage, we also have a duty to dignify our spouse and never make her feel uncomfortable.
And Allah knows best.
