canklecat

Before making any major equipment changes, try some latex tubes (I use Silca with the smooth plastic valve stems) and more supple tires. Might make your existing bike more tolerable for awhile.

I use puncture resistant tires on my hybrids but for my road bikes I prefer a better ride over puncture resistance. I just avoid most high risk zones while riding. I've had very few punctures in three years.

I really like Conti Grand Prix Classic skinwalls, an updated version of a 1970s-'80s tire with a thin but effective puncture shield, excellent grip and durability, and very thin translucent sidewalls for ride quality. After more than a year and a couple thousand miles I'd buy 'em again. Adding latex tubes a month ago improved the ride quality significantly.

And I do a lot of home physical therapy, following most of the exercises I got from a PT clinic this time last year when I was in PT for two or three months recovering from injuries (my C1-C2 are permanently damaged from a 2001 car wreck, and my shoulder was broken and dislocated from a 2018 incident when I was hit by a car). Really helps. I don't use any equipment other than some 20 lb jugs filled with water. The Bowflex channel on YouTube has lots of good, short videos on exercises that don't require special equipment. Best videos I've found for basic DIY PT.

bargo68 

I have a Cannondale st-1000 with 32mm Panaracer tires at about 60 to 65 psi and it rides great! It's fast and nimble for how long the wheel base is, and the frame is stiff enough to slightly counteract any "squish" from hard climbing with larger, softer tires. Maybe try taking all the racks and fenders off your Cannondale and see what it comes in at. It will never be like some of the newer TI/carbon endurance bikes you're being recommended, but you might already own the bike you're looking for!
If the rear dropout spacing is 130, you have a load of options for new wheelsets and drivetrain combinations!

wvridgerider

I prefer steel. If you get a frame nd fork you can cut the steerer tube cut to the hight you want.