Search problems: tag not found; when found, not returned in date order

(1) I have several posts with the tag “humor”, and I have a few containing the actual character string “humor”. When a (potential) visitor enters my site URL a la “mydomain.com/humor” the result is a “not found” and when the word “humor” is typed into the search field, only a subset of relevant posts is returned.

(2) Upon any search-field search, the obtained results are not by original post date.

It is to be noted, FWIW, these posts have been migrated from a wordpress.com site at which they were earlier migrated from a blogger site! So these posts have had quite a journey. Yet they retain their original dates. However, also, each has been edited more than once (to make various corrections to html, for example). Yet, still, they retain (as listed in display of post) original post date.

If at all relevant, the template is a heavily modified version of Jeff Starr’s H5 template.

IF I can correct these problems, how would I go about it?

Site is apfwebs.com