1) Ignore the instructions and let it sit for 24 hours. 4-5 works, but there will still be a lot of lactose in it. 24 hours is needed for lactose free. Or almost lactose free really.
2) The easiest is just skip the started packages all together. -if you're being fully SCD compliant just find a regular plain yogurt with only these listed on them (Lactobacillus bulgaricus, Streptococcus thermophilus) They are the basic base for all yogurts. Asto Balkan Style is an example depending on where you are located:
astro.ca/products/astro_original_balkan_plain_750g_family_tub/#.UapS4ECcFww The cultures are not listed, other than it just says "bacterial cultures" but I wrote to the manufacturer to verify it's just the two bacteria mentioned above and they responded listing them as the only ingredients.
The difficulty is that a lot of store bought yogurts don't always list the culture, so at first it can be a pain in the butt and a lot of searching to find the right one.
Anyway - to make a batch of yogurt all you need to do is add 1/2cup of this (i.e Asto Balkan or other brand) instead of the powdered yogurt starter and stir it in well. Perfect yogurt every time. Very smooth, light and creamy when made with 3.5% milk.
Most yogurts made with only these two cultures have a very mild taste... when other cultures like acidophilus are added to it, the yogurt will become quite sour. Honey takes care of that though.
Anyway - there's lots of starters out there - just takes a bit to find the right brand in a store close to you.
3) no there are no commercial SCD yogurts.