O.M.
Umm, yeah . . . sounds familiar!!! I can soooo sympathize with what you are going through! (My son is ADHD; now 10 in the 5th grade.) I can tell you from experience that structure is key. Lists are great-- morning checklists; bedtime checklists; chore list; homework lists-- the "list" goes on! LOL. Also try to avoid any major changes in schedule or routine, if possible.
As you prepare him for kindergarten, you might want to think about putting him in a Montessori school . . . The kids are allowed to work at their own pace, and the relaxed setting allows for ultimate concentration. They are completely engaged in the lesson b/c of the hands-on materials. They often sit on the floor when they do their work, which eliminates the issue of sitting still.
Changes that we made in diet included no dyed red foods; whole grain in the place of white bread for school lunches; no sugary breakfast foods (oatmeal or shredded wheat instead); peanut butter was apparently good for him; we even sent caffeinated drinks in his lunch at one point b/c apparently children who are ADHD don't become hyper with caffeine, but instead are calmer and able to concentrate better.
All that you are dealing with could just be immaturity (especially the personal space problem), and will likely improve with age, but I would urge you to not rule out the possibility of medication in the future. They have many medications that metabolize within 5 hours, so by the time your kid goes to sleep at night, his last dosage of medicine is completely out of his system. (I honestly felt worse about giving my kid the caffeine or aspartame in diet sodas! But he may very well be a more extreme case.)
But as you continue to observe your child and research the issues, you will know what's best. Just don't question or blame yourself, b/c that can be a brutal game. You're obviously on top of things as a Mom, or you wouldn't be working so hard at finding what is best for him
:-) O.