The fell runner you have a pic of in full flight (with 745 number on) is a friend of mine and he is something else on a downhill - don't be put off fell running they are a great bunch and will encourage anyone who's giving it a go.
Can't help with the weight sorry as mine is stuck and doesn't seem to change no matter how much I do.
Think about doing core strength maybe if your getting twinges it may help and watch how fast your building your long runs.
Did 11 miles yesterday putting together different bits of trail to make up another new route for the future - erm not 100% sure will be trying it again in a rush you just don't realise how hard some of the hills you happily plod down are when you try to go up them instead. Had a farm dog run out at us a bit aggressively on one bit when I'd not long nearly killed myself slipping in the mud then we encountered another hill and I had a slight meltdown at that point. Several emergency jelly babies and a hug later I felt much better. Did decide to run in on the bottom road though rather than up the TMW killer hill will save that treat for another day