This must be played very slowly and with deep expression. Take a lot of pauses, some of them very long.

Come, thou fount of every blessing,
Tune my heart to sing Thy grace.
Streams of mercy, never ceasing,
Call for songs of loudest praise.
Teach me some melodious sonnet,
Sung by flaming tongues above.
Praise his name - I’m fixed upon it.
Name of God’s redeeming love.

What I am emphasizing is a plea for God’s enabling Spirit, a realization that the fountain of blessing and mercy was bought by streams of Jesus’ blood. For this reason, I play quite soberly, reflecting on the high cost of God’s blessed Spirit for us. Play with a heavy anguish, not sweetly. Be forceful in places to express loudest praise sung by the flaming tongues of angels who are ever in God’s presence.

The mordents are played first on the principal note, then the mordent, then a hold again on the principal note.

Keep things separate. That’s what all the commas and slash lines are for. Note well the sudden pianissimo in the next to last measure.