Philip, I haven't played Sanford - I'm a Tobacco Road apologist personally.
Since I don't know the course, I don't totally trust my eyes to read the photos on HistoricAerials.com. However, they do have a 1965 aerial that appears to show the course in a 9 hole format. The clubhouse appears to be in the same location as today, and there is also a hole or two where today's driving range stands. The west end of today's driving range tee lies on top of an old Ross green, while another green was buried or abandoned on the west edge of the range itself maybe 115 yards ahead of today's tee. It looks like most of the new hole corridors are on the outskirts of the east and north ends of the property. There also appear to be a few new holes in that original course parcel, as will be explained further below.
A few notes on comparing the aerials against the current scorecard follow. Again, remember that I've never been on the property so my observations may be way off:
* If 8 was the original opening hole, it stopped being so prior to 1965 as the clubhouse is clearly in the same location today.
* The northern lake on the course was not there in 1965, nor was there a green just at the southwest edge of it. It looks like the hole playing through the corridor of today's hole 1 played on to today's 3rd green, so your observations on the second half of that dogleg appear correct.
* 8, 9, 10, and 18 look to be the only holes on the course that roughly follow their original corridor.
* There was once a par 3 just east of 9 that played to a green located very near the fairway bunker on 9 today. I'll call it hole X. I suspect there would have been a tee just right of that hole that then played on through the corridor of 1 up to the current 3rd green. I'll call it hole Y.
* In the corridor of today's 7th, there is clearly a green well short of one near the road today that I'll call hole Z. I can't tell where it teed off from, but I suspect it was in the clearing in the trees just behind the current third green. It appears there was at least a five hole loop that went hole X, hole Y, hole Z, current 8, current 9.
* There was a hole that appears to have played from the current 13th green, roughly, to the left side of today's driving range tee. Let's call it hole N. It looks to have been followed by a short par 3 that played from somewhere near the middle of today's driving range tee to a green in front of today's 10th tee that is now part of the driving range, which I will call hole D (for driving range). Today's 10th likely originally had a tee much closer to the water's edge. This gives you a four hole loop to complement the 5 hole loop above, this one going hole N, hole D, 10, and 18.
My best stab at the original routing is that it went hole N, hole D, 10, 18, hole X, hole Y, hole Z, 8, and 9. I would guess, looking at the photos, that the guy who told you 8 is the original hole 1 was misinformed. However, it is plausible that there could have been a clubhouse between Z green and the road, somewhere near where 7 green today is. It just seems unlikely to me, unless hole N originally had a tee closer to where the clubhouse sat in 1965 and still sits today. I doubt Ross would have had such a long transition from 9 green (which would have been 2, hypothetically) to N tee. Sadly, this leaves only four roughly original holes on the entire property, and only five original greens.
If you haven't already, take a look at HistoricAerials.com and do a search for 600 Golf Course Rd, Sanford, NC and see if you see something else in the 1965 aerial. I could be way off base and I'd like to hear from a set of eyes that have been there.