Substitute for sesame oil

Sesame oil has such a distinctive flavour, I'm afraid there's nothing that will give you exactly the same taste. Many sites suggest peanut oil, but this is more or less tasteless in my experience.

I would suggest toasting some unsalted peanuts or cashews and adding them to the stir fry, to get that roasted, slightly smoky flavour. Just add them to a warm, dry pan and toss frequently to prevent burning.

If you're feeling really adventurous you might even try smoking some peanuts (you can do this in a wok with certain wood chips and a bamboo steamer, plenty of instructions online).

Unless you are getting your beef directly from a farm or butcher's truck, most blood will long have vacated the muscle. As the muscle enters rigor mortis and is (this is true for America and Europe, traditions and techniques are different in some parts of Asia and Africa) hung for the prescribed seven to ten days it loses almost all of its capillary blood.

Dry aged (not as common) beef has this effect even more, if you purchased a supermarket filet with a "sanitary pad" in the bottom, the moisture you see there is juices, water and some protein, from collapsing cells, not blood. The same is true for any beef not cooked to shoe-leather consistency, the reddish "juice" is intra-cellular and not from blood vessels.

As far as flavors go, soaking your meat for any period of time below, let's say, two days, has very little effect. It was traditionally done to apply some osmotic power to the cut in order to dilute and remove salt left over from the drying process (this was before cooling was widely available, still done in many countries outside of Europe and America), but isn't usually necessary for meat you get in the meat aisle or from your local butcher.

As far as tenderizing goes, no. Enzymatic tenderizing (that is the stuff that happens when you age beef) goes on, of course, but you won't be able to tell much of a difference between the time you bought the muscle and the time you consume it. Water itself does not tenderize. Minutes to hours do nothing.