The only way to really know gender is to look under the cat's tail.
Un-neutered males are pretty obvious.  Neutered males and females can
sometimes be confusing, but generally, if there's anything on the
outside below the anus, it's a male.

If you are really interested in caring for this cat, you need to get
it secured and to the vet for a thorough checkup/spaying or neutering/
and vaccinations.  The vet will be able to answer a lot of questions
about age and background and could probably tell you if or for how
long the cat has been on the streets.

The key will be to get it secured without risking injury (physical or
psychological) to you or the cat.  I think you are doing the right
thing by establishing the relationship through the trust of food
(provided you aren't leading it on!).  Keep trying to gently make
contact until you are comfortable getting ahold of it.  Eventually,
you'll be able to get it in the carrier to the vet.

Unless you live in the country, and your cat is used to living among
wild animals and defending itself, cats should always be kept
indoors.  If you have no other pets, young children, or house plants,
the process is fairly easy.  Place food and litter box in a small room
and leave the cat there.  Eventually allow it to explore other parts
of the house until it's comfortable everywhere.  Like dogs, cats are a
big responsibility, but every cat is a unique pleasure.

Finally, there are only two ways to really treat a cat for fleas:
topical ointments and oral pills.  Oral pills aren't nearly as
effective, but can be useful when there are infants in the home.
Either way, you probably need to have the cat firmly in hand to
administer.

A alpha male feral cat in all his glory is a spectacular thing,  I
honestly and truely do not know how you can domesticate one of these
guys and  bully should you even demand to castrate one of these mighty
cats.  They are so damn bold.  I have one that appears in my garden
every once in a while and he is not even that big.  He will just sit
there and stare at me until I approach him, his head like a big jack o
lantern daring me to come nearer.  And he is just a minor lord.  Ive
seen huge 20+ pound feral cats in the inner city.  Like are you doing
them a favor  by taking them inside forever or what?  I think they
like their life the way it is but of course, 3 meals a day and plenty
of catnip is enough to turn anyone's head.

If your visitor is truly feral, then I must say that after only 3
weeks you are making absolutely remarkable progress.  You could have
the makings of a lovely relationship there if you are patient.  It can
take a long time to domesticate a truly feral tom if that is what he
is.  The main thing is to respect whatever limits he sets for you,
even if they seem to change on a daily basis.

Best of luck to you and him/her/whatever.

--tension