Do pants indicating they have 7% wool, among other materials, require checking for possible linen fibers?
Isn’t the shaatnez of today of Rabbinic order, since a deOraytah requires that it be carded, woven, and twisted, something apparently not done today, if so, wouldn’t this be a safek derabanan lehakel?
According to the Rambam and the Shulchan Aruch (Yoreh De’ah 300:1) only one of the three conditions you mention is required, so that if a linen thread is sewn into a woolen garment, there would be a full Torah prohibition.
This does not mean that there is a full obligation to check every garment with 7% wool, and this depends on other circumstances. In particular, the 7% might be “batel” before the linen is threaded, so that the Torah prohibition won’t apply. This will depend on how the garment is made. An obligation will only apply where there is a reasonable chance of shatnez, and this depends on factors such as country of origin, brand and quality, and so on.
It is probably best to consult with a local expert, who will be able to advise more concerning specific items.