One of the users mentioned Gita Press, which is a good translation. Here is the link:
Another is by Parimal Publication, Delhi. Here is the link:
Rajaji's version is an abridged one. It is good, but it ...
In Ayodhya Kanda it was mentioned that before constructing their hermitage on Chitrakuta mountain, Sri Rama, Sita and Lakshmana met Sage Valmiki.
इति सीता च रामश्च लक्ष्मणश्च कृताञ्जलिः |
अभिगम्याश्रमम् सर्वे वाल्मीकि मभिवादयन् || २-५६-१६
After deciding thus Seetha, Rama and Lakshmana all with joined palms approached the hermitage and offered ...
Valmiki and Vyasa were present.
Valmiki was given a boon by Brahma that he will know all the incidents in Ramayana and he can write an epic on it. More details in this answer.
As for Mahabharata, this answer goes in more detail.
Sri Hanuman approaches Sri Raama and Lakshmana in the form of an ascetic.
कपि रूपम् परित्यज्य हनुमान् मारुतात्मजः |
भिक्षु रूपम् ततो भेजे शठबुद्धितया कपिः || ४-३-२
Casting off his monkey's semblance Air-god's son Hanuma attained the persona of an ascetic, for that monkey is incredulous in mind about Raghava-s
Sri Hanuman speaks to them while ...
According to popular legend, Tulsidas had originally planned in writing a Ramayana in Sanskrit. However, Lord Shiva appeared in his dream and instructed him to write it in Awadhi language.
In fact, in the Bhavishyottara Purana, Lord Shiva tells Mother Parvati that Valmiki will reincarnate in Kali-Yuga as Tulsidas to compose Ramayana in a vernacular ...
If you are looking for an English translation of Critical Edition of Vālmīki Rāmāyaṇa, you can buy:
The Rāmāyaṇa of Vālmīki: An Epic of Ancient India: 6 Volumes in 7 parts
by Robert P. Goldman, Sally J. Sutherland Goldman (mlbd.in)
The Rāmāyaṇa of Vālmīki: An Epic of Ancient India, Volume VII: Uttarakāṇḍa (amazon.com)
You can borrow Vol. 1, Bālakāṇḍa at ...
The OP stated in the question that Sītā is portrayed as Rāma's half-sister in the Jātaka.
However, the story of Jātaka in question clearly states that Of his sixteen thousand wives, the eldest and queen-consort bore him two sons and a daughter. So Sita was mentioned as the own sister of Rama-paṇḍita.
The question itself indicates that the questioner had done some deeper study of Ramayana and in his/her post script, the questioner called for a well-researched answers.
According to my study I had understood that
a) Bala Kanda contains major interpolations
I. Prologue to the story
The first 4 Sargas of Bala Kanda. It is in these Sargas we will come ...