I haven't read the whole thread, so this may have been said.
Growth scans are not the most accurate measurement (there is a degree of difference between operators, measurements can be distorted by position of baby, maternal body weight and a number of othe factors), although as a rough guide it is useful.
On the plus side, baby is active and as you haven't mentioned it (other than the anxiety) I assume you feel well and don't have any medical conditions that are effecting your pregnancy. I'm also assuming you've had cord flow dopplers done, liquor measurements done, as well as a CTG (checking babies heart rate) done if indicated and that these are all normal. The only thing is that the growth isn't as good as we'd like. If that is all accurate, then I think you are ok for now and I would not push for induction, as it is not necessary (judging on the information given) and may to lead to complications (or failure of induction).
But it is worth talking over with your MW/another MW and your obstetrician to see if they can out your mind at ease. Weekly scans and dopplers etc are a good idea and should pick up any problems early.
I don't think your obstetrician would be too keen to induce if all other tests have been ok, baby is active and mum feels well, if a little anxious. If the growth continues to tail off dramatically, then they may well advise induction.
It is true that warning signs are reduced fetal movements (although remember they do have rests), you not feeling well, bleeding and/or pain (obviously) etc. But try not to get to obsessed with counting the kicks, as it may well drive you demented!
Unfortunately, nobody can guarantee that things won't change/go wrong in between scan dates and so on, so I'm not saying there is no risk- just that at present all looks ok. It's about balancing risks- risks that something might change between now and next scan VS risks to you and baby of early induction that is not medically indicated now.
All I can re-iterate is make an appointment to see your MW/A MW you trust and/or your obstetrician and explain your fears. Hopefully they will be able to explain things in more detail and re-assure you.
Best of luck OP!