My cats played at first now they fight?

When I got my female kitten I introduced her slowly to my 10 yr old male.I did the towel rub/scent thing to make sure they had a good chance to get along they were kept separated for a week and introduced several minutes at a time until I felt safe(same with the Lab that I have)--and at first they played a lot-now that she has gotten older he is mean to her he rarely wants to play and hisses and growls and really goes after her--I know that he likes other cats he always seems to have friends outside and he always wanted to play with my female I had before that passed away(she hated other cats and did not play with him) I am heartbroken the kitten is sweet as can be and I wanted them to get along and am so disappointed This male goes outdoors ONLY because if I don't let him he used to spray and tear up the furniture(and YES he IS fixed) so now he comes in to eat and then afterward she tries to play and he mainly just growls hisses and then wants back outside(I have a basement and he can get in through a cat door we put in for him and it is warm in there and I made him a nice bed of old blankets and pillows and a storage bin so he has it pretty good that way!) but I just don't understand why he has changed so much toward the kitten he never liked me anyway only my husband and he still gets a lot of attention from my husband- the female is mostly like "my" cat The dog gets along ok with both He grooms the male cat and he lets the female lie on his big pillow with him although when they fight he doesn't like it! --If anyone who is really experienced with cats can give me some idea why this happened and any ideas to have them get along better I would sure appreciate it! Have been thinking about a Feliway but they are expensive and don't want to throw my money away--All are treated with Frontline now(where at first the kitten wasn't as she was too young) could this be making the male hate the female as it changes her scent

Thanks in advance for your answers