Low gears!
I see your bike list has 2010 or older bikes. The 2010 Cannondale Six came with a 12-25 cassette, like many road bikes of the period.
Now, 11-28 is standard, and 11-32 comes on many bikes. I changed to an
11-32, it "just barely" fits on my short cage Ultegra derailleur, even though it's past the recommended range for the derailleur.
I can ride up 8% - 10% grades staying seated now. At a slow speed, below 4 mph, it's a very low cadence, but it's a moderate pedal pressure. I can climb much longer hills without burning matches. And the low gears are nice for spinning up an easy to moderate grade.
It's possible to retrofit an older bike with a long cage derailleur that accommodates bigger cassettes.
Long climbs
It's
all about pacing if the
gearing is low enough. I'd rather climb a 1500 foot 7% grade than do 5 repeats of a 300 foot 7% climb. There's no temptation to sprint near the top, just set a pace and climb steadily. And the big climbs tend to be scenic, too.
That 3 mile long, 8% average climb sounds challenging to me, but very doable. I've climbed up the similar grade, 4 mile long Mt Mitchell park road with no problems.
Blue Ridge Parkway: you
need to go ride it! Near Asheville, it's all climbing and descending. But the grades are mostly 8% or less, often 6-7%. It's extremely scenic. And there's scenic overlooks during the climb. Just a quick stop at the overlook is helpful. I think most any rider that can ride 60 miles on normal terrain can ride 40 or more on the Parkway. Dial back your effort, and enjoy the ride. The downhills are very nice, mostly with sweeping turns that need little braking. There's few water sources on the Parkway, so some route planning is helpful. Don't ride up from Asheville, that can be busy. Start at an overlook up in the high country.
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Training
I don't like scheduling training rides. Instead, I do group rides most of the time. Some groups are a little faster than me, so I put out hard efforts to not be "too" far behind on the climbs. And it's the best motivation for me to ride at least 2-3 times a week, I have to keep up my fitness level.
Analyzing with Golden Cheetah
If you like stats and ride analysis, the free, open source
Golden Cheetah is great. ( It's not too useful without a power meter.)
Just upload ride recordings, and it plots lots of graphs and stats. Then you can adjust the graph settings later to be more useful to you.
I use the CP chart, Critical Power. It shows my best efforts at all time periods from 5 seconds to the longest ride I've done. And the current ride shows on the chart, with percentages of the best times. I have a pretty good idea of my 1-minute, 5-minute, 30-minute power targets.
I have a "Ride stack" page, with time on the x-axis, and stacked charts for power, speed, cadence, heart rate, elevation, grade, and
W' Balance. W' is essentially the estimate of much your power reserves are being temporarily depleted by hard efforts.
I can drag the chart to make a custom interval to review -- a hill climb, a fast paced section, etc. Or have it select the top 5 efforts for power at a selected time interval.
These intervals can show on the included route map.
CG calculates kilojoules for the ride, a good number to use for the
calories burned. I tend to be close to 30 calories per mile on a spirited ride. Bikes are efficient!
GC trends:
I have two years on the Trends - Stress chart. It shows aerobic and anerobic trends, long term and short term, quite interesting. I can see the longer rides and harder efforts in May showing up as a big increase in the chart. (It's "training stress", so more is better. Racers can use it to peak at the right time.)
Early last spring, I was feeling "slow", "sluggish", "weak" and wondered if I was "losing it". But the trends were similar to the previous Jan-Feb trends. I'm back to normal now.
There's many more GC features that are useful for formal training, but I rarely look at them.