Hi Fred
I managed to find a full copy of the book , which only showed partially on google books, on a site called archive.org, which was 'Les Protestants d'autrefois:sur mer et outre mer' by Henry Luhr originally published in 1907. This roughly translates as "The Protestants of Past Times, On and Over Seas."
This seems to be a work of research into 'forgotten' Protestant heroes of France, both natives and foreign born, and there is a 4 page section on Maria Jean Von Hügel's father (which seems to suggest their branch of the family at least were Protestants). Her father is never named in full but was born circa 1737 in the parish of St Guilliame, Strasbourg, France, (Where his father Brigadier Von Hügel was based) and joined the army as an officer at 16. He was sent to India and distinguished himself in 1760 in the rank of captain at the seige of Madras, and went on to command his own regiment of French Hussars in India which fought alongside Hyder Ali (
http://en.wikipedia.org/wiki/Hyder_Ali) and The Dutch East india Company against the British East India Company in the two Mysore Wars.
Maria Jean was actually born out in India, in Tranquebar, in 1767, and sent back to Strasbourg to be bought up by her grandparents, the Brigadier Von Hügel and his wife. She was married to Jean Henri Wildermouth in May 1784, when he was based in Strasbourg as a Major in The Duc de Sang Sang's Strasbourg regiment. The only extra information given on him (Wildermouth) is he was a holder of the French Military Cross, and that he was the primary source of information the author had on the life of Marie Jean's father Captain Von Hügel. Apparantly the Captian had died in India some time before 1788, and at that time back in France the ageing Brigadier Von Hügel was concerned for his grandaughter's future well being and therefore desired his own military pension of 150 Francs a year to transfer to her on his death (he was 77 at the time). Wildermouth wrote on his wife's behalf to the Minister of War to add weight to the Brigadier's plea with the account of her father's sterling service on behalf of the French Crown in India, and his subsequent ill treatment by the Dutch East India Company, but the outbreak of the French revolution the following year seems to have meant his plea went without any official reply. (Though of course we do know by 1831-3 she was on a state pension double that of her late grandfather so all seems to have worked out well in the end).
Of course since Marie outlived her husband, and from his army records he was likely considerably older than her, around 40-45 at the time of their marriage, and she 17, it is unlikely if Jean Henri is your man's father, she was the mother. I'm thinking perhaps she was a second marriage to the father and stepmother to any existing children?
Also I assume you have already downloaded the existant baptisms for the family at IFHF website?
www.rootsireland.ie/They have the following baptisms showing:
Church Baptism Wildermoth James 1828 Roscrea Parish (Roman Catholic) Co. Tipperary (fathers first name William)
Church Baptism Wildermothy Michael 1834 Roscrea Parish (Roman Catholic) Co. Tipperary (fathers first name William)
Church Baptism Wildermouth Daniel 1837 Roscrea Parish (Roman Catholic) Co. Tipperary (fathers first name William)
Full details cost 5 Euros to view if you havn't already.
There is also this:
Church Baptism Wildermuth Elizabeth 1804 Parish of Birr Church of Ireland (Protestant Anglican) Co. Offaly (fathers first name John)
It is a Protestant baptism, but not far from Roscrea, about 15miles/20km North. Cant' find the 1787 Belfast marriage on the site, but presumably that would have been Protestant too, as I do not believe Catholic marriages were legal in Ireland until the emancipation acts of the 1820's (though I stand to be corrected there)
Anyway certainly a fascinating family here, and pleased to have been able to help in some way. Do keep us updated with any progress with Jean Henri's military records. I would be interested to know if my hunch is right in linking these families. Certainly the French sources nearly always spell it 'Wildermouth', which as you say was far less common form on the continent than Wildermuth, and in itself seems to add some weight to the theory the two families in France and Ireland are linked.
Regards
Richard