Hi - a few things.. Everything the other posters are saying is true.. but whats really missing for me is what kind of rider you are, and what kind of rides your doing. Your bike apparently comes with 25c tires stock, which tells me its more of a recreational bike. If your more of a recreational rider, that tire just may suit you and your bike better. That being said, I've only run 23c tires, and can't imagine going to 25c or larger. I'm 200lbs, 6'2, and I've never felt unstable on my tires. I ride paved roads, which often are pretty beat up after a bad vermont winter. Lots of potholes, and often I hit patches of gravel/debris. I've ridden on the occasional dirt road as well.
My guess is that you need to improve your bike handling -- what kind of debris was it? How did you negotiate it? What tire pressure were you running? (this can be crucial). Especially on a road bike, knowing how to shift your weight and steer through debris is crucial. You can't just hit gravel and steer as if you were on a hybrid bike -- everything needs finessing. Most people I know find 23c as the sweet spot for tires, so there is no reason you should not be able to ride them and feel comfortable.
So, my answer largely falls into the category of "you need more practice, and time on narrower tires".. That of course goes with saying that if you are trying to ride 23c tires at 80psi or under, or are on dirt roads/gravel, you need to either up your air pressure, and/or rethink your tire choice.
Well I've only been riding a couple of years. Weigh about 190 now but put on a few recently. Should be lighter.
Tire pressure is 120. LBS told me keep it at max for climbing. I do lots of climbs. Recreational/endurance rider. Very hilly area. All paved roads but plenty of potholes.
I love the 23's. They feel better. Just a little less stable. Maybe its me just getting my legs back. I did not notice it before the accident. Plus my cyclocomputer was not working after they trued the wheels, so I think I may have taken the turn faster than I thought I was.
Anyway, this was why my #1 option was to get used to it.
But one follow up question for you. When you said the bike was more recreational, I agree. But I wouldn't mind it being faster. I can mostly keep up with my friends on better bikes. Can often more than keep up, but don't mind a little extra edge until I actually ugrade.
Sounds like your spot on.. I think you just need more time. 120lbs tire pressure is doable, but alot. I used to ride at 120 as well, but have recently found the advantages of dropping to 105 to 110. Its counter intuitive, but there is a point where more air pressure leads to increased resistance. If you search this site on tire pressure, you will get tons of info. I suggest you drop down to 105 - 110 psi. It will give you better cornering, and better shock absorption. 120 psi is rock hard for clinchers - another reason you could have wiped out. Also - what kind of tires did you put on? Hopefully you were able to get something decent.. While i'm not an authority on tires, I think that its one of those items not to skimp on.
As far as the last paragraph you wrote - you never actually asked a "follow up question".! Just because your bike is more recreational, no reason you can't make it faster, or especially, get faster yourself. To "make" your bike faster, best upgrades you can make are a seat that is comfortable, handlebars/stem that have proper reach, and then lighter wheels/tires. It occurs to me that if your bike feels unstable, it may not fit you correctly! Watch some you-tube videos on proper seat height and fore/aft adjustment. The fore/aft part is often overlooked, but should not be. Once you get positioning to a good starting point, meaning, your legs are mostly extended at the bottom of the pedal stroke, and the front of your knee falls in line with the pedal axle when your crank is at 3:00 -- then you can fine tune to what is comfortable. How do you feel the fit of your bike is??
It sounds like you are just getting into riding, so the best thing you can do is just ride.. get used to your bike, how it handles, etc... 23c tires should be the choice for you, as far as I can tell from your riding and goal descriptions.