[Aiwendil]

A house was built for him upon the southern walls

In the 'Attack' section, we have switched the escape of the exiles from 'south' to 'north', in accordance with the later idea that Idril's secret way went north instead of south, as in the old story. But here it seems quite probable that the secret way was made in the south because that is where Tuor's house was. So would it not make sense to change 'southern' here to 'northern', and keep the connection between the position of Tuor's house and the secret escape route? This would also fix a problem I recall noticing in the later sections, where, after having escaped from the city, Tuor and the exiles turn and see his house on the near side of the city. Putting his house on the north would allow us to retain this (otherwise it will have to go).

In these days came to pass the fulfilment of the time of the desire of the Valar and the hope of [the] Eldalië

This change was, I think, gotten rid of. There's no reason for the (purely stylistic) insertion of 'the'.

for in great love Idril bore to Tuor a son and he was called Eärendil.

Perhaps we should insert here some mention of the mother name "Ardamire" from Shibboleth. I can think of no other place for it, and it would be a shame not to include it at all.

straying in the mountains alone was taken [prisoner] by some of the Orcs prowling there

I think this is good, but I think we must at least consider the implication of the Tale of Years D2: "Maeglin captured by spies of Melkor (Sauron?)"

Of course, the suggestion of Sauron can easily be disregarded as a projected change that cannot be implemented (particularly because of the question mark).

Also we may have to work in this from the Tale of Years C: "511 [>509] . . . Ulmo sends a last warning to Gondolin, which now alone is left; but Turgon will have no alliance with any after the kinslaying of Doriath."

There is no previous indication that Ulmo sent a last warning to Turgon, but as this comes from some of the latest writing on the end of the First Age, it carries a certain weight and cannot be easily disregarded. Of course, we have no idea how Ulmo was to send a last message. But perhaps it would be enough simply to say that he did, and leave the method ambiguous.

Whether we do so or not, this quote brings up another interesting point. Note the words "but Turgon will have no alliance with any after the kin-slaying of Doriath." Christopher Tolkien comments that this could mean "no alliance with any son of Feanor", and I think this interpretation quite likely, considering that the kin-slaying of Doriath is named as a reason. But what has this to do with the message of Ulmo? If Ulmo's counsel is simply to abandon Gondolin and depart down the Sirion, there is no logic in Turgon's refusal: no one is asking him to have an alliance with the sons of Feanor (or with anyone).

The only explanation I can think of for an unwillingness to have an alliance being a reason for Turgon's refusal of Ulmo's counsel is that the old element of Ulmo's advising Turgon to go to war was either retained or revived. And on a close inspection of the sources, this seems not all that unlikely. In the last account of the Fall of Gondolin, that in Q30, it was retained. The only piece of evidence that it had been dropped is the Grey Annals, where, in an extremely compressed account of Tuor's coming to Gondolin, it is said that "There Tuor was brought before King Turgon, and spake the words that Ulmo had set in his mouth, bidding him depart and abandon the fair and mighty city that he had built, and go down to the sea." Certainly it sounds here as though the advice to go to war was dropped; but when one considers that this was a rather compressed account, that it's the only source indicating such a change, and the implication of the Tale of Years, it begins to seem quite likely that the first component of Ulmo's counsel was not dropped at all.

So perhaps we should consider adding that element back into section 2. Of course, even in the presence of evidence in favor of this, we could still decide that the mere likelihood or possibility of the rejection of this element necessitates its omission from our text.