1st focal reticle do not hinder long shots in any way shape of form, to ge honest i wouldn't use a 2nd focal.
but you do want a reticle that is thin enough not to cover to much of the target when the shots get long.
I use a 4-16x50 PMII from S&B formy long range stuff.. it has the klein reticle, which is plenty thin for long range but not to thin that its unusable when the light gets low.
with that 1.5-6 set on 6 you'll be ok out to the distance you mention, the width of the reticle at its thinnest part corresponds to 6.5mm @100m . thats about the same as my illuminated mildot on my 3-12x50PMII,, which i've used to take roe deer out as far as 620m.
having said that,, since getting the klein (gen 2 mildot) in the 4-16 i wouldn't want to go back to the normal midot for the longrange stuff.. the klein covers 3.2mm or so (i forger exactly, but its just over 3mm) at 100m. so its about half the thickness of the other reticle,, and is an advantage..
Pete