That #3 condition may be significant.
With the mixture screws, winding one out individually should give you a response from lean to rich if you go completely outside their range, say 1/2 turn out to 2 1/2 out, which is what you'd expect to see.
What you are looking for is one of them that doesn't have that linear response, indicating that the carb is not clear for that low speed metering. If one is impaired when tested like this then it won't matter what the clean ones do as they'll not overcome the irregularities from one poor performing carb.
That #3 would be the initial suspect.
The revs so unstable suggest that one cylinder is erratic in firing, which would give you that pulsing as it chimes in/ out.