But the underlying contention -- that the south's economy was reliant on slave labor -- is true.
To that point, the plantation owner could well produce a 1000 (or more) bales of cotton. But twenty of the smallholders were more likely to produce something like 50 bales of cotton, not a comparable 1000. A standard bale is 500 lbs -- and that is a whole lot of cotton to pick.
Per the National Cotton Council...
Cotton bolls range in size from under 3 grams to over 6 grams per boll. Seed accounts for about 60% of this weight; the remainder is lint. This translates into about 200 to 400 bolls to produce a pound of lint, or 100,000 to 200,000 bolls per bale.
Pre-Civil War, figure 3 grams per boll (or less). Thus, the simple logistics of a cotton harvest (not to mention the tending) severely limited a smallholder's productivity.
The fact is that the primary agricultural crops of the early south -- cotton, indigo, tobacco, etc. -- were all extremely labor-intensive, thereby lending themselves to a plantation economy. There was a reason why slaves had been introduced into the south in the first place. Which is the same reason why the south's economy remained shackled to them -- until, finally, machinery changed the equation.
http://news.nationalgeographic.com/news/2003/01/0131_030203_jubilee2_2.html
All your examples concerning cotton relate to an era several decades after the 1790s. During the 1790s, tobacco was the main southern crop in Virginia and NC and cotton was grown mostly in SC and Georgia. And the territories that became the other southern states hadn't even been opened for very much settlement.
At the time the Constitution was written, the economy of the southern states was totally reliant on slave labor.
The remark relates to the 1790s, not 1850. Much of central Alabama was still inhabited by the Creek Indians until their defeat by Andrew Jackson in 1814. The cotton growing south didn't exist in 1790.
Which was my original point and still is my main point. So there's little point in continuing this.