Hiya Lynne!

OK... first off I am the same build as you... long distance but suck wind on hills! What I have found is the only way to get strong on hills... is to climb so I found a decent uphill that was a mile long and I'd do intervals on it... up and over, turn around, up and over, turn around... I do some weights but there is nothing that helps your climbing ability like climbing.

the second part of your question is long argued... to me a flat is just that... looks like my dining room table. And what is easy to one person is not easy to another... some "hills" I refer to as a rise... some as rollers (those you can just push over by standing and sprinting) and then there are hills... I consider a hill anything where I have to really gear down and work to get to the top...

as to the cadence thing... you want to be pushing and maintaining speed while spinning some decent circles... the problem with pushing a big gear is that while it feels fine now, you may, in time, blow up your knees. Really MOST of this stuff is unnatural when you're new and takes work.

to me it sounds like you're doing just great! give it time... all of this is a learning curve!!!