I've installed a little Bruce oak pre-finished in my house and as a table top for my church. It was fine. I'm sure they supply lower quality pieces sometimes but my boxes were good. Essentially all pieces were usable. Realistically that is the risk. I can't imagine a box that is all unusable, but a few pieces is possible. If you are worried, buy an extra box or two and take back what you don't use - that is a good thing about the big box stores. I've also put down >600 bd ft of pre-finished Hickory, I do not remember the brand. That also was fine. I've also taken up old oak. From that experience I am confident that staples hold much better than cleat nails. But either would work. But the staples are cheaper and easier to find - which may be an indication what "professionals" use.
Glueing flooring down is not for solid wood, it is for engineered floors. I've done those too. Staples over rosin paper is what I recommend.
Forget about the joist direction. When you go perpendicular the boards span several joists and it can help transfer load and make the floor a little more solid. But unless you have deflection issues now you won't with the hardwood down. When you can go across joists, it is a little bit better but both ways work.
I bought a flooring nailer/stapler from Harbor Freight. I've since loaned it out. It leaks a little now but still works. It's cheaper to buy your own than renting a nailer unless you can do it all in a short period of time. The flooring nailer will not work much in the hallway, however. You have to have room to swing the hammer and hit the trigger for the nailer. Several boards on both sides of the hall will have to be fastened with a finish nailer. A 16 gauge will work, a 18 gauge is too light in my opinion and a 15 gauge is best (again in my opinion). Again, HF is a good inexpensive source. The 16 gauge will be significantly cheaper than the 15 and will still work fine. You have to face nail against the wall and can then switch to nailing through the tongue.
Take extra time to get the first row straight, I recommend chalking a line. Your walls are probably not straight. Don't install tight to the wall, leave a 1/4 inch gap. It will be covered by shoe. That molding also helps to disguise things a bit. I would measure across the hall to know if the walls are parallel. Again, they probably are not. I'd figure out a plan before I started nailing. How many rows will it be and how much do you have to cut the last row. If it's a lot, you might want to rip the first row some so it looks more symetrical. This could result in significant flooring loss, however.
Most pieces were straight enough I could just bang them in but if you don't want to throw away flooring be prepared to pry some into position. I liked driving a large straight blade screwdriver into the sub floor to pry with. Crude but quick and effective. Especially in the middle of a room, it's hard to find something to pry against but this will work.