When I was pregnant with DD1 I craved Guinness so my OB let me have one a week (how I looked forward to Friday evenings for my weekly drink ) as he said the stress of not having it was probably worse than having it - I think that is what your FS is saying with the one coffee. So if you feel you need it, relax and enjoy it.
i agree with this
if you're worried about how much caffeine, maybe make it a little weaker if you can stand it

i was told by a neurologist to drink a glass a coke a day as a preventative for migraines (two drugs - one worked, one didn't - only variation was the caffeine - and the $80 a month price difference!) - i tried to cut out coke entirely (don't drink coffee - yukko!) - but it just started migraines again. the doctors said i was better off keeping that one coke a day and not having the withdrawals and migraines. over the first month of my pregnancy with DD, given the horrific morning sickness, i ended up weaning to one glass every few days, then one a week, and then nothing til i was about 8 months gone and the headaches started coming back.

with that waffle - my point! don't try going cold turkey - you will feel worse for it. if you are personally concerned about the caffeine levels, maybe work to reduce your coffee to a single shot instead of a double or something kwim?