Hymn Ai am fy meiau i

I discovered the following hymn here. At first I thought it was by Elias himself and then by a namesake but having looked again I think it is by the man himself. I have attempted a translation. The tune recommended is Cranbrook. it is under the section of the hymn book considering "Angau Crist a'i effeithiau" - Christ's death and its effects.

Ai am fy meiau i
Dioddefodd Iesu mawr,
Pan ddaeth yn ngrym ei gariad Ef
O entrych nef i lawr?

Cyflawnai 'r gyfraith bur,
Cyfiawnder gafodd iawn;
A'r ddyled fawr, er cymaint oedd,
A dalodd Ef yn llawn.

Dioddefodd angau loes,
Yn ufudd ar y bryn;
A'i waed a ylch yr Ethiop du,
Yn làn fel eira gwyn.

Bu 'n angau i'n hangau ni,
Wrth farw ar y pren;
A thrwy ei waed y dygir llu,
Trwy angau, i'r nefoedd wen.

Pan grymodd Iesu ei ben,
Wrth farw yn ein lle,
Agorodd ffordd, pan rwygai 'r llen,
I bur drigfannau 'r ne'.

Gorchfygodd uffern ddu,
Gwnaeth ben y sarph yn friw;
O'r carchar caeth y dygir llu,
Trwy ras, i deulu Duw.

Did he for my mistakes,
Great Jesus, face such plight,
When, in power, his love came down
To earth from heaven's height?

The law so pure he kept
To justice true he stayed;
The massive debt, although so great,
In full he now has paid.

Obedient on the hill,
He suffered death in woe;
His blood the black Eth-iop-ian cleans
As pure as pure white snow.

His death it is our death,
Through his work on the cross;
A legion, because of his blood,
Through death to glory pass.

When dying in our place
He, Jesus, bowed his head,
A way he made, through the rent veil,
To heaven's pure abode.

He conquered a black hell,
The serpent's head he bruised;
Through grace, from jail, to join God's own,
He brought a legion loosed.