Dear Nice and Naughty,
For someone who doesn't consider herself a girlfriend type, you've sure got yourself a whole shitheap of men. God only knows why this dating shit always seems to work out that way.
You're right — it is a little too late to be tactful, and this should teach you a lesson about the importance of being upfront. Open relationships require advanced ninja-like levels of honesty and disclosure. If you can't handle that with casual dating, how do you think you'll do when it's someone you really dig?
If David really is that into you, I doubt he'll be thrilled to hear about the guys you were seeing while he was on (and off) tour. If you want to keep dating him (which I strongly question in the first place — he doesn't exactly sound like a casual-relationship kind of guy), I'd tell him sooner rather than later, and be prepared for some major backlash. The but-we-never-talked-about-things excuse is going to sound pretty lame, and you know that, otherwise you wouldn't feel so weird. Just because something hasn't been explicitly spelled out doesn't mean there isn't an understanding or expectation from one or both parties.
On the off chance that David still wants to date you, I would look beyond his circle of friends (and Robert's, for that matter) for any future dates. Yes, it's hard to keep your hands off band boys, but no one wants to be known as the next Yoko.

Dear Waiting,
This is a sad one, and I wish I had something more for you than a long-winded version of "Keep waiting, dude." But that's what you need to do if you're genuinely interested in seeing this thing through. People who are grieving need tons of space and don't always make the best relationship material. It's pretty tough to say "Why aren't we doing it more?" or "Spend some time with me, you jerk!" when a significant other's mom is in hospice. You tend to come off like an ass.
That's not to say that you should settle for being ignored. You have certain emotional needs, and it's unrealistic of her to expect you to shelve them until she's ready to be a couple again. Barbie and Ken may work that way, but not people. Think about what would help you feel better during this difficult period. Is it a commitment from her to check in every few weeks, even if it's just a quick phone call? An understanding that you two aren't going to date other people unless you talk about it first? Once you've figured out what you want — and made sure it's not too taxing on her — go ahead and ask for it.
The worst she can do is say no. Then you'll know that, despite your best efforts, this coupling may be missing one key element of all successful relationships: timing. Unfortunately, that's one thing you can't control.

However, I still feel like he has little or no sex drive. Fearing rejection, I'm afraid to initiate things. But when he initiates, we have good sex. I'm used to guys who are all over me (because they're guys — I thought that's what they do). I feel like he doesn't want me. So what do I do? If I try to talk about it more, I risk disturbing an already-delicate situation. But I also know that in new relationships, it takes some time to let loose and get to know each other more intimately. — Bah