Sorry you are having such a worrying time, gingerbreadman. There's nothing like worry about your baby.
My DS's talipes was discovered at the 20 wk scan along with some other 'soft marker' for trisomies. We had amnio and all was clear, chromosome-wise, but when he was born it was clear that he did have talipes, and missing parts to his foot, and a missing fibula.
I did find the STEPS website very helpful and joined the forums there - it seems quite quiet these days but you only need one informed friendly voice to make a difference.
Talipes - always daunting to see your baby have treatment but the babies adapt and are happy while we have all the stress, and the treatment is very successful.
Missing fibula - DS does just fine. The main issue was that a missing fibula often comes with the leg being shorter, and he has had bone lengthening surgery. Again, daunting while it is going on but also very successful.
A barely there femur sounds potentially more complicated, but I don't have any experience so can't say.
Are you within reach of London? I think you can self refer to the Harris Birthright Trust Foetal Medicine centre at King's, which is a top NHS scanning and research centre. They will be able to give a second opinion in the scan and tests and offer immediate amnio if you want it.
When they found DS's lower limb issues they arranged for me to talk to the Paediatric Orthopaedic Consultant shortly after the scan, and she was very re-assuring and practical.
My DS has a splint and a bit of a shoe raise, is missing bones, toes, half the muscles and tendons he should have in his lower leg... he skateboards, was fell walking and abseiling last week....