I posted a few comments awhile back.... actually years ago.... 3-4 weeks in the primary is pretty normal, going longer is ok. Kind of like you stated, if you let the yeast drop out you might have too add bottling yeast.
I switched to kegging and that issue is a thing of the past. I personally don't like adding yeast a second time. I'd rather bottle condition longer and at a higher temperature. You can also rouse the yeast every few days too. Shake the bottles.
Key, I think is try to bottle within 6 weeks for a session beer. If I was add yeast at bottling I'd do "Muntons Premium Gold" for compact sedimentation. Sometimes you just have to do it for big beers.
Take look at published yeast flocculation percentages. Flocculation is about how much stays in suspension. Lower numbers will be more forgiving on carbing as the beer sits waiting for you.
Also weigh out your priming sugars, boil water, and bulk prime if you're not doing this already. A common rookie problem with priming is volume measurement vs weighing. Go to a gram scale measurement for more resolution, accuracy, less rounding. Don't forget about your total priming volume if it's more than 5 gallons you might need bump up the priming amount.
As for dry hopping, I always do a 2ndary. I like my beer clear and without sediment. That said, dry hop no longer than two weeks other wise the beer will get a grassy taste.