First off, you might consider a faster film or a film with better reciprocity characteristics like TMX or TMY. TMX is faster than Tri-X for long exposures, interestingly enough.

In computing the exposure, you want to figure reciprocity last after basic exposure, filter factor, and bellows factor. See what that gives you.

Why do you need the filtration? Usually you would use a yellow or orange filter for a landscape, and not so much indoors unless you are photographing some brightly colored objects that would appear the same in B&W and you want to get better separation between them. You might also use strong monochromatic filtration to reduce chromatic aberration with an old lens or the single cell of a convertible.