I'm North of Dallas, have a house on heavy clay soil. Foundation watering is critical around here, not an option. I had a system put in a few years ago, it's hooked up to the sprinklers so I can just set it and forget it. I can share some things with you that might help..
I routed around the patio, but was advised to add a double loop there so I did that. Only a few feet of extra hose. The driveway feeds a 2 car garage, we did the same things there. Bring the hose close, loop it back so you have parallel hoses about 6" apart.
18" may be too far away, my literature search indicated 12" would be better. Depth matters a lot, though - to get water around the edges of the slab you have to get down far enough so the lawn won't steal the moisture and so it doesn't have to take forever to percolate. I would be concerned that a few inches depth might not do much in terms of effectiveness. Remember that soaker hose volumes are small, and once the hose is buried you get hydraulic lock VERY fast - the hose fills up then the flow rate plunges as the water has no where to go. So you then turn the water off, wait 15 minutes for it to settle, then you have to hit it again. This still only puts down barely 1 ounce of water per foot on average per cycle. I run my system on auto twice a day, every day. In other words, if you are going to do this manually, you have to be at the valve every day during the hot season for the watering to make any difference.
The check for enough water is to drive a stake down about a foot and pull it out. If the clinging soil is moist, your probably ok. Do this at 3 or 4 points around the perimeter of the house.
Also, don't use a flat garden soaker hose, they don't work well when buried. Get a real 1/2" diameter self-cleaning soaker hose. They're cheap. Whoever you find that sells them will be able to get you an end cap. You don't need a blow-off, just remember when you open the bib to be slow about it. As for the end-of-hose to bib connection, you may have to rig up something but that shouldn't be hard.
You can get Y-s with vavles on each side from a plumbing supply house.
Good luck, Bill