I think you're being much too hard on your Newport 17.
I disagree completely with the hard to sail conclusion. In fact, I think the boat is easily single-handed as well as being blissfully uncomplicated for any inexperienced crew you may have.
The low displacement to length ratio, and the resultant conclusion of a bad ride and difficult to sail is a generalization that may not apply either to your sailing area or your boat. If you're out in the heavy stuff she'll not ride as well as some other boats of differeing hull forms, displacement, or length. On the other hand, she's easily sailed solo and you need only the lightest of air to get her moving. While other "more seaworthy" boats are essentially becalmed you'll be sailing right along. While your hull speed is lower, you'll achieve it much more easily and in much lighter air. In fact, you'll be reefing in conditions that heavier boats just get moving in! You'll also find that your boat is far more nimble than many others; she'll respond quicker and accelerate quicker.
As to your capsize number and heavier seas. You'll want to make sure that you can secure your keel in the lowered position in the event of a severe knockdown and potential roll over. You really don't want it slamming back up into the keel trunk and you certainly want to preserve your righting moment in such a circumstance.
You can do something about your ability to avoid capsize as well. If you do not have a reefing system, install one. Can your companionway hatch be closed and secured? What do you have for washboards? consideration might be given to increasing the size of your cockpit scuppers and drain lines. And when venturing out you can reduce the volume of your cockpit, which will decrease that capsize number, by filling it with stowed and secured gear. That big ice chest you may want to carry will take up a significant volume of cockpit space and that is space that water cannot fill when in a capsize situation.
And you may well see six knots. Chances are it will be downwind and surfing!
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.