Miles,
I am very glad to have your analysis. For the 1 July unit movements, I have relied heavily on the detailed account of Samuel Pickens, in Voices from Company D, ed. by G. Ward Hubbs. Pickens writes that his regiment (5th Alabama) was at a fence and that a battery was 150 yards in front. I believe that fence is shown on the 1876 map, because Captain Page's four Napoleons fit nicely for the mentioned battery. But after guarding the gap on the left for a time, Pickens writes that his regiment went forward to join the brigade at another fence, "and there our Company was sent forward to a barn to act as sharp-shooters," relieving North Carolina men there. A fence is shown on the map 750 feet north of the McLean barn, which fits Pickens' description. The reason I say O'Neal's attack began from that location is because Pickens writes: "After the Brig. passed on we ran out of the barn & through an open field where the bullets were flying thick & went down on the left to a lane where the Regt. was." A lane does run north-south from the McLean buildings to the Mummasburg road. Pickens continues: "I never saw troops so scattered & in such confusion. We were under a heavy fire from the front & a cross fire from the left & pretty soon had to fall back to a fence where the Brig. was rallied by Col. O'Neal & Gen. Rodes." Pickens account is mirrored by an opposing account of the 45th New York regimental committee found in New York at Gettysburg I:378-379: "The Alabama brigade alluded to, advanced steadily to the left without heeding our fire much, whereupon Captain Irsch sent word to Dilger's Battery, asking them to engage the Confederate infantry ... the enemy began to break and run up the slope of Oak Hill towards McLean's barn." The 45th scooped up a considerable number of prisoners. ADAH records list at least 35 men from the 5th regiment who were captured outright on 1 July.
During the evening of 2 July, I am of the mind that Ramseur, Iverson and Doles were in Long Lane (where they remained) while O'Neal and Daniel were in the open behind them, but the latter two brigades did move back into town for several hours before heading to Culp's Hill, perhaps on West Middle Street (west of Baltimore Street). But you have me regarding the 5th, which did not accompany the brigade to Culp's Hill as you point out (it would help if I double checked the facts first). Still I believe we are mainly in accord, although other historians have different views. While Harry Pfanz's book, Gettysburg-The First Day, is pretty close, David Martin, in his book Gettysburg July 1 seems to suggest that the 5th was committed separately, but I think it moved together with the 6th and 26th. The 12th Alabama on the right would have been mostly shielded from view of the 11th Corps and appears to have remained roughly in place until Ramseur's advance. The 3rd as you note, fought separately, first with Daniels' left regiments and later with Ramseur's right wing.