1) To me, those "cuttings" in the foreground look overly ambitious. I would take two, maybe even 3 cuttings from that one large one in the front. Too much foliage will lose too much moisture to transpiration, even with water conserving rosemary leaves. And the baby roots, when they start to grow, won't be able to support them. I cut off the tip 1/2 of larger leaves (I think I did this even with the rosemary). I don't remember why you don't just cut off the entire large leaves -- maybe it has to do with hormone production by the older leaves (?). These older leaves usually yellow and drop off some time during the rooting process, their work done.
2) I can't tell for sure, but these look like shallow trays. Sand combined with the shallowness suggests to me a very quickly drying medium (you DID say there are drainage holes right?) As I mentioned, I usually allow for about 3" of stem in the soil to grow roots from. This means 3" depth of growing medium (what I use, I described before). I feel 100% sand dries too quickly and is hard to keep evenly moist. Deeper growing medium means there is a gradual range of moisture levels, and hopefully, the cuttings will root at their preferred level.
4) Leaves should be completely removed from portion that is below and immediately above soil (cut or pinch off not pull off which can strip too much bark/outer layer) Contact with moist growing medium will encourage those leaves to rot.
5) There should be a leaf node at the very bottom of the cutting (i.e. cut just below a leaf node). I also like taking hammer-shaped cuttings with attached whole main stem or a cutting with part of main stem attachment shaved off (for which there is a name but I'm drawing a blank -- ah! I believe they're called "heels"). As much as possible, I like to have two nodes below ground to ensure root growing points, especially with cuttings that don't (easily) produce roots along the stem.
6) Ideally, the leaves should not be touching the humidity cover. Condensation will form inside and can cause the leaves to mold/rot. When using plastic bags, I recycle disposable take-out Asian food chopsticks. Wire coat hangers could be fashioned into hoops. Humidity covers should have ventilation holes.
p.s. Personally, I don't like Perlite as a growing medium. They almost always very quickly grow green algae on them and while I can't say for sure, in my experience, the algae seem to be detrimental to new growth -- seedlings or newly rooted cuttings.