Still claiming to be a new rider (august 30) - how long can I get away with ignorance and lack of experience as an excuse I wonder???

am not and have never been keen on exercise for its own sake - have to do something with purpose and since leaving school only regular 'sport' was competitive horse riding - you need core strength but really is only muscle control rather than exercise - the exercise is simply the 'jobs' that go with it - so cannot claim to have ever been an athlete......
I am still in the dark about how my riding is going and how my body is responding to regular exercise - i am 169 cm tall and started off weighing 67.5 k. (bmi approx 24) so nearly overweight and feel heavier than I would like.
Now after riding on average 150 kms a week I am up to 68-70 kilos on a bad day.... I admit I am hungry but have been trying to eat really sensibly and cut out the bad stuff especially anything that comes in a packet - and that means no icecream!!!..... starting to bug me - i am keeping a food diary and use a garmin so realise that it takes a lot to burn calories - only about 200 odd after 25 km ride -
I am 52 - is that the main problem do you think - i know its what goes in versus what goes out but really a bit of encouragement would be nice. I'd like to get back to 60-63 kilos. that was my normal weight when living a very active life on the farm - physical work though not exercise except horse riding 1 hour per day.
also I am very very slow - only just started to average 23kph over the regular 25 k loop - (no real hills) and that was 'racing' some poor guy on a mountain bike who was about 800 mts in front of me and had no idea that I was using him as bait to chase down.

i am working on my rpms - 80 to 90 average - but to achieve that I still have to be on the small ring in front, and in the middle on the back - so that means I am not putting much power through the pedals -and that means less speed -is that right? Sorry I am still trying to come to grips with the physics of cycling.
stamina wise I am OK, have done two organised 100km rides in two weeks and do a 50k plus at least once a week,also try to get up to noosa once a week and do a small hill up there - its a 3 km steady climb - can do it - 3 times with about 5 mins break at the bottom but still mainly on granny gear and flat out keeping to average of 11 to 13 km on the up. try and take off one day a week = i am told recovery is important -
am going to get some help from a cycling coach in 2 weeks to try and get a better understanding of the gears and how I should use them, but feel like a my age I have to keep on trying on every ride - mind you in spite of lack of results I really do love the bike and getting out on it every day - its just looking at the results that gets my goat.
anyway would appreciate any tips on what else I should do - especially the weight thing - my aim is to eventually (how long is eventually!!!) get to an average of around 30kph - I think that would be respectable but it seems impossible at this stage - maybe should review it down!
Maybe I am just too damned impatient?? retraining this old body may take a lot longer than I thought? anyone else started at my age and can share tips, experience would be great.