Ok, so I'm trying to figure out how best to use my 15 minute skill bonus, and have concluded that the best thing I can do is complete a whole ton of missions, and turn them in en masse. This, however, presents and interesting puzzle... a question of what order I should turn them in. Naturally, the SP for each mission scales back as you level up. I'm currently CP8, and I want to have UA by Sunday (or at least try to).

So my question is this, is there a formula for calculating the scaling of skill points? like if a mission is worth, say, 300SP with my level matched to the mission, how do I know what it'll be 2 levels higher... or 10 levels lower for that matter?

I think the 15 minute boost only applies to missions you have accepted after activating the boost. I don't think you can complete missions than use the boost to get more skill points. I could be wrong on this, but I am pretty sure that's how it works.

In the case that I am wrong, it won't matter what order you turn in the missions. To answer your other question, I don't know of any formula but I'm sure it isn't difficult to figure out.

You can accumulate completed missions before activating the skill point bonus. However, I don't believe that it really matters which order you turn them in. In my experience it seems that the mission rewards are locked based on the level you were when you took the mission. Thus, the most you can do is use this to determine when to take certain missions that have high rewards, because you will still gain a lot of XP just doing the missions.

If you haven't already run the FE mission chains, those will cause you the most grief since you need to turn one in to get the next, leaving only the last to get the bonus toward. For the most part mission XP is static or actually increases based on your level for scalable ones like the FE's. And make sure to run all easy repeatable missions before turning it in.

Also, remember that the XP Bonus timer doesn't count down while logged out. You can use this fact by positioning yourself by an short repeatable mission like Cold Comfort before activating it. That way you can do a couple additional runs of that under the bonus by logging out under the mission cool down. Of course, this only makes sense if you have other things you actually want to do outside of game during that time.

Good Luck