There are two prohibitions you refer to:
Any acts of affection, temptation and stimulation are forbidden; that would include hugs, kisses etc (see Shalom's answer).
Wasting seed - if any activity leads to discharge it is also forbidden (see pron).
AFAIK, there are no differences for this prohibition in having relations with a Jew or a non-Jew as the verse says "ואת זכר לא תשכב משכבי אשה תועבה היא" - namely a male, not "your fellow" or "your brother", just any male.
To clarify the subject of wasting seed, as Rambam explains in the Mishneh Torah, Laws of Prohibited Sexual Intercourse, 21:18 that this means bringing about any type of ejaculation which is not at least potentially going to result in procreation of the species. That the Prophet Isaiah equates this with murder!
It is forbidden to release sperm wastefully. Therefore a person should not enter his wife and ejaculate outside of her. A man should not marry a minor who is not fit to give birth.
Those who, however, release sperm with their hands, beyond the fact that they commit a great transgression, a person who does this will abide under a ban of ostracism. Concerning them, it is said (Isaiah 1:15): "Your hands are filled with blood." It is as if they killed a person.
This is also the view brought in Shulchan Aruch, Even HaEzer 23:1-2.
That the commandment to Be Fruitful and Multiply, which was given to Adam HaRishon and is thus incumbent on all mankind, has two dimensions to it, the positive aspect of preservation of the species (which pertains to Jews because they have positive mitzvot) and the negative aspect (which pertains to both Jews and non-Jews) of not becoming involved in these procreative actions when there will not at least be a possibility for procreation.
And to clarify further that this concept is in the context of preservation of the species specifically, the words of Rabbi Chaim Vital in Sha'arei Kedushah, Section 2, 6:10 are enlightening:
Wasteful seminal emissions are worse than spilling the blood of others, for in doing so, he is spilling not only their blood, but the blood of all their future generations without end.