Dear Ludmilla:
I can´t answer your questions I must say at first! But maybe give you some thoughts I had while reading your question. I have checked some facts and it seems that there were no church records in Landa before 1748, but of course there can be other records and not at least, written documents both in nearby parishes (which probably included Landa at that time) but also in private letters and other notes that have been written down.
Another thought I had was; if your ancestor had participated in the 30 Year War, could he be found in these war records that must be at Riksarkivet (The National Archive) in Stockholm (or other archives from that time, war records etc.) a problem seems to be that during the fire at the old royal castle Tre Kronor in Stockholm (in the end of the 17´s centuary) many documents and books were lost, but not all...
You also use the older swedish word inhyse which I think means that he lived at someothers property or participated in their farming or so? But it excisted also a kind of institution called soldattorp ( a kind of smaller cottage where the soldiers lived during time of peace) where these soldiers had their small household often with their families still staying under time of wars (but many families were also participating in the services lines following the armed forces, called in swedish Trossen. A very well known history about this is Bertold Brecht´s epic drama Mutter Courage, describing what happened to these women and children during the 30 Years war...(it has probably also been written alot of more scientific historical books about this if you search for it).
I hope somebody here at Anbytarforum have any connection to your ancestor and will find some more to say in this case! I hope all the best because I am like you searching alot of disapeared ancestors and relatives in other european countries, many lost in war or the archives etc. that have been destoyed!
Sincerely yours: Steve