$1.00 a foot delivered isn't a bad deal. Buying bulk I can get the price on LMR-400 down below $0.60 a foot, but that doesn't include connectors or shipping. As always, make sure it's a reputable source. Some sites claim to sell "equivalent" cable, but it's sometimes low quality Chinese stuff.
Yeah, as for the additional cost, investing in better feed line is rarely a bad idea, unless you really go overboard. RG-8 or LMR-400 is a good choice for what you are doing. Going much beyond that would have very negligible benefits, and the cost goes up quick.
Sounds like a good set up. Tilt over is a good way to go. Way too many people get injured or killed installing antennas. Antenna height is really important. Having some altitude at your home is a benefit. Using the tilt over mast to get the antenna well up above the surrounding obstructions will be a benefit, too.
Yes, grounding, 100%. While you are digging the hole to sink the base, run in at least one 8' copper clad ground rod. You can get these in the electrical isle of your neighborhood hardware store. Leave a few inches up above the ground. Get the properly designed clamp to go with the rod. You need to run a heavy piece of copper wire from the base of the mast to the ground rod. Secure it well. You also should install a lightning arrestor on the feedline before the coaxial cable enters the house. This is actually NEC code, although most don't bother to do it. This likely means that you'll want your coaxial cable in two sections. One section from the antenna to the lightning arrestor, the other from the lightning arrestor to the radio. There will be a place on the lightning arrestor to attach the ground wire (6 gauge or larger). Run that direct and as straight as possible to the ground rod at the base of your mast. There are a number of rules about grounding, and I don't have space to go into them all here. It would be a good idea to take a look at the National Electric Code and see what it says.
http://www.theantennafarm.com/catal...mount-631/1-5-700-mhz-with-uhf-connector-637/
This grounding will help reduce damage in the event of a direct or even nearby lightning strike. Lightning doesn't have to directly strike your antenna to do damage, so keep that in mind. Your location on a hill is going to raise the risk. It's going to add a bit to the overall cost, but the safety side of it makes it worthwhile. Doing it now when you are doing the original install is going to save some headaches.