Baby Back Ribs on Gas Grill

Hey guys, I'm looking to cook some baby back ribs on my gas grill tomorrow.  I figured I would use dry rub, use indirect heat and cook on low for up to three hours.  I have a few questions though.

1.  Since I have three burners, should I leave one or two burners on?  Cook on the middle grate or one of the side grates?
2.  Do I need to put the ribs on foil or can I put them directly on the burners being there's no flame beneath?
3.  What the ideal grill temperature I'm aiming for - 225 to 250 degrees?
4.  I'm skeptical about burning propane for three hours.  Being it's on low, how much of my tank will it really eat up?

I appreciate any advice you can give me.  I've always done ribs in the oven, so this is new to me.  Thanks in advance!

I have done regular ribs with dry rub on my gas grill - takes hour or less on low - turn every five minutes. I make one rack and use two of the burners with direct flames.

We do not use foil - they go directly on the grill - watch for grease flare ups if real fatty

I put my ribs on the center grate/burner with indirect heat.  I leave the left/right burners on.  Takes about an hour or so depending on the amount of meat on the ribs.  I also use a dry rub until they test done, then I use  sauce (usually the Bone Suckin' Sauce brand from Raleigh, as it doesn't have MSG or HFCS). 

Even with 2 burners on (I shoot for a 350-400 degree temp with the indirect heat) I can do several sets on 1 tank fillup.  If you have a spare tank, I'd have it filled, just in case.  I usually run mine for awhile, then I go fill the empty "spare" so if it does run out, it's a fast change.

I did a set at my mom's house last weekend.  She only has 2 burners, so I put the ribs on the right side and used only the left set of burners.  We also put a drip pan under the right side and put water in it... other than that it was as I usually do them.  These came out even better.  I think having the water helped steam them and made them much more tender.

I do one end burner on low, the other two off. Try to maintain a temp of 225-250. put ribs on the other side, close the lid and leave them alone for at least 4 hours.

I have 4x burners, I keep 3x off and only 1x on low at the far end.  I put a little tin foil plate of soaked apple wood (or whatever) by that burner and try to keep it about 200-225. 4-6 hours you're golden.  It ain't old school, but with practice can get impressively close for those without an actual smoker.