Help on controlling the AI please

[Imp]

I will admit to being a bit ambitious in my first proper foray starting with defending a port from attack while the Marines land (or not) so I decided to try something a bit smaller with special forces scouting a lab then using same map to attack it as they spot Chinese advisors & scientists (hopefuly) which is when I ran into problems. Setting AI as defender the relief force that turns up from nearby barracks as reinforcements just sits there. Which is why I asked do they need waypoints assigned to move or should I set to meeting engagement but then my thinking says I need to set defenders reaction so they do not leave there posts.
The problem with this is I then have to guess when they should move to take back flags (well try)
Thats why I asked if reaction 99 was a special case as in what AI uses normaly. If I set reaction to quite high for them like 2/3rds way through if they lose enough flags will they still go early?
It will take a while for me to playtest & find out so was hoping someone who has done could advise me.

Also on reinforcements having arrival turn vary slightly by setting arrival chance to say 30% sounds good but set reinforcement units individually. Do the individual units check for arrival or the platoon leader & all or none turn up because the first case splits up the platoon so is of no use.