Acceleration = sluggish & sputters

Recent changes to my 1994 Saturn SL2 Twin Cam 4dr:
1. Fuel filter replaced
2. O2 sensor replaced
3. Spark plugs replaced
4. Oil change
5. Throttle body cleaned
6. 2 or 3 cycles of fuel injection cleaner (used Lucas and another time used Marvel Mystery Oil)
7. Tires checked, with proper psi

Check engine light has never come on, and car has almost 102,000 miles on it.

Problem(s):

When I accelerate to 30mph or above, the car is very slow to accelerate. It also jerks forward in a weird seizure-like motion, like a stutter, but very obvious. I push the gas to 3500rpm and you can hear the engine rev (which probably mystifies neighboring drivers who think I am challenging them, when in reality, I am going not even 30mph), but you can't feel the car speed much at all. It'll surge forward and then struggle to accelerate again.

Sometimes, when I have the gas down to 3500-4000rpm, the car will do the repeated jerk as it ever so slowly accelerates, and it feels like I'm going over a rippled median strip. Merging into highway lanes is hell! Speeding up after slowing down or leaving from a stop is also hell, as it does what I just described, or it does what I said in the 1st paragraph.

I know this hard acceleration is putting unnecessary wear/tear on my car, but I don't know how else to speed up with the flow of traffic, and even then, acceleration remains terrible.

My current mechanic, who I have been going to for the last decade or so, even test drove the car, revved the engine, coming to the conclusion the O2 sensor needed replacement, which he did. That was the last repair/replacement on my car, and it didn't change the acceleration problems.

Also, when I'm at idle the car vibrates in spurts. I don't know if I'm describing it accurately. Annnnd the car shakes when I do highway driving, but I assume I need to get the tires aligned/rotated/balanced?

ANY HELP would be appreciated and my apologies if any of these are repeat questions. Please send me links if they are old questions.

Thank you!

Also, a couple days ago, the steering wheel was so forgiving that I overturned on a left turn and had to right the wheel like a beginner driver. It did it on several occasions, and it was a rainy day. Any more takers?

Thank you again!