Hi Mark again,

The christening date you gave for John James Callister son of Wm Callister & Amelia or Emily Crellin of 10 Jan 1843 (IGI 448045) is a member submission and may not be reliable. However there is an IGI baptism extracted from the register for John Callister s/o William Callister & Emily Crellin on 10 Dec 1843 at K German.

How do we know this is the JC who married Elizabeth Clucas on 5 Jul 1866?

Fisherman/tailor: I was hoping someone would double check the 1871 census image I quoted previously for John Callister, 24, of German, on the vessel "Catherine" where the profession (presumably when not fishing) could read either Joiner or Tailor, which might help match him up with a family, whether he continued with tailoring/joinery or not.

The IGI has extracted entries for the following which may or may not be significant, but pretty much match up with Margaret Skelly's grandchildren in 1861. Esther also fits as d/o Thomas & Margaret in 1851:

Esther Callister d/o Thomas Callister & Margaret Triggor (transcription error?) c.30 Jun 1850 K German
Thomas Walter Callister s/o Thomas Callister & Margaret Greggor c.19 Jun 1853 K German
Emily Callister d/o Thomas Callister & Margaret Greggor c.25 Apr 1856 K German
Edward Richard Callister s/o Thomas Callister & Margaret Greggor c.12 Jun 1860 K German [at a stretch could "Richard" be mistranscribed as Beecher?]

There is an IGI extracted marriage for Thomas Callister & Margaret McGregor on 4 Nov 1848 at Braddan. This is after the expected birth year for John. However there is also:

John Griggor s/o Margt Griggor c.17 Jan 1847 K German IGI ext

I still think your best bet would be to see what is actually written in John & Louisa's marriage record in the parish register.