1. After reading up on underpitching, I'm wondering if I should get another vial and pitch it also?
For pitching a vial without a starter, a 14+ hour is to be expected. While you certainly could pitch another vial, I'd probably just let it go as it is and exercise patience.
2. If so, is there a particular method to use for this, or just open the bucket, add yeast, stir?
Yep, that' pretty much it. I'd recommend careful stirring so as to not introduce too much O2 into the beer.
3. I don't know if I have any activity yet, I don't hear any bubbling, but am using a blow off tube, rather than just the airlock, so am also wondering how I tell- do I just wait, or do folks routinely take the lid off and look?
I take the lid off and look, but I wouldn't worry about it at this point. You may not be seeing any bubbling because the lid isn't on completely tight. Not a big deal.
4. Last- I also realized (after more reading) that I have a lot of trub left in my beer, I see that this can both help and hurt my beer, I'm trying to keep it cool to offset any nasty taste, but is there anything I can do now aside from this to minimize eventual bad taste?
Another thing to just not worry about right now. I admire your attitude and desire to get all this stuff right, but trub just isn't that big a deal, especially for a beginning brewer. My advice would be to sit tight, give it 24 hours, then carefully take a peek under the lid. My guess is that you'll see fermentation at that point. Keep working on it for future brews, but remember the homebrewer's mantra...Relax, Don't Worry, Have a Homebrew! Or a good craft beer since this is your first batch!