I found a partial answer to my questions in this post Re: Switch between FAST and SLOW adevrtising
The min / max advertise parameters are there to set a random function range.
Didn't find the answer on Apple guidelines maximum 1280ms. Anyone could help on that ?
Is there any issue except slower connexion to set a min 3000 and max 4000 with some old IOS versions ?
These parameters are specific to Apple. Can you kindly check Apple forums for details on these.
The link above explains the interval times as being ideal for maximizing connection speed, thus as you are suggesting, longer intervals/times will only slow down connection, but won't necessarily fail to work.