> it was the same for me, the language feels very different by 1300.

The language in section 1300 isn't much different from section 1400. Almost all of it is still good English today if you give the words their modern spelling:

Then after much time spoke the Master, and his words were cold as winter is. His voice was as the crying of ravens, sharp and shrill, and all that heard him were adread and durst not speak.

"I deem¹ thee to the death, stranger. Here shalt thou die, far from thy kin and far from thine own land, and none shall know thy name, nor none shall thee beweep."

And I said to him, with what boldness I might gather, "Why farest thou with me thus? What trespass have I wrought against thee, that thou deemst¹ me so hard a doom?"

"[Swie!]"² quoth he, and smote me with his hand, so that I fell to the earth. And the blood ran down from my mouth.

And I [swied],² for the great dread that was come upon me was more than I might bear. My heart became as stone, and my limbs were heavy as lead, and I []³ might no more stand nor speak.

The evil man laughed, when that he saw my pain, and it was a cruel laughter, without mercy or pity as of a man that hath no [rewthe]⁴ in his heart.

Alas! I should never have come to this town of Wolvesfleet! Cursed be the day and cursed be the hour that I first set foot therein!

¹ We still have this word in modern English, but the meaning is different.

² No idea what this word is.

³ I assume the ne in the text here is required by some kind of grammatical negative agreement with the rest of the clause. In more modern (but still fairly archaic) English, nothing goes here. In actual modern-day English, the grammar of this clause isn't really available for use, but it's intelligible.

⁴ This turns out to be the element ruth in ruthless, and a man with no ruth in his heart is one who is literally ruthless, without "ruth". It literally means "regret", but the use in the text clearly matches the metaphorical sense of the modern word ruthless.