Having read the History of Parliament biography I would say that not only has the epitaph writer gilded the lily, he has also attempted to rewrite history. Sir John indeed had many roles (line 15), not all of them successful, but in order to match any of his appointments to the allusive and flowery language of the memorial I need to know more precisely what the memorial says - ie. data before interpretation.
Line 8:
This seems to be two thoughts: Pater Maritus Filus Optimus - "father, husband, best son" referring back to Sir John, and Charles the second doing the appointing referred to in lines 9 and 10. Is this valid, or is the writer praising the King?
Lines 9 and 10:
My crude translation: "(Charles the Second) appointed Sir John to a three man body dealing with armaments and a more secretive Council and after this was successful appointed him not long after to be chairman (governor) of a five man body." The most obvious correspondence to Sir John's actual career would be his seat on an ordnance commission formed after the death of Sir William Compton in 1663. The Parliament biography says the ordnance commission was so successful, the King nominated Sir John to the Treasury board ("Quinquevir Aeravi praetor"?). Could "Secretioribus" be an attempt to latinize "secretary" and the line is saying Sir John was secretary of the three man armaments council, or are there two entities involved?
Line 25:
Does "Aetatis Suae LXIV" mean aged 64 or in his 64th year?