1. generally the standard is to hold a mobilization for 2 minutes (stretching is generally defined as something different than what we do here).  you can hold for more, like up to 10 minutes. you may also feel good effects in much less time, like 15-30 seconds. the recommendation is to do these mobilizations at least once every day, and if you have time, do them multiple times a day for areas that are restricted. keep in mind that some mobilization and smashing work can create trauma, so the guide is that something generally should feel better, not worse after mobilizing or smashing. if it does feel worse, back off and check the next day, and/or back off on the pressure or amount of time, or use a softer tool until you adapt somewhat. then increase time/pressure/hardness of tool as you adapt.

2. is that the DB/KB stretch that is lying down? can you point me to the one that you are referring to?

3. it can take as a little as a day to release something, or it can take many months. some areas will require you to think about the other 23 hours of the day to really make a change, like shoulders that are rolled forward which will only be fully addressed if you also think about what you’re doing at your computer, driving, looking at smartphone, etc. the amount of time it takes depends a lot on the problem itself: how long have you had it, how severe a problem it is, how your body position/posture is in the other 23 hours of the day, etc.

4. there are smashes for the lower back, and some mobilizations which will affect the lower back since all of them address the body as a system and not just in one place on the body. my favorite is the supernova on the QLs.