Overthrow not (mē katalue). “Destroy not,” “do not loosen down” (carrying on the metaphor in oikodomē, building).
The work of God (to ergon tou theou). The brother for whom Christ died, Rom 14:15. Perhaps with a side-glance at Esau and his mess of pottage.
But it is evil (alla kakon). Paul changes from the plural Koinéa to the singular kakon.
With offence (dia proskommatos). “With a stumbling-block” as in Rom 14:13. This use of dia (accompaniment) is common. So then it is addressed to the “strong” brother not to cause a stumbling-block by the way he eats and exercises his freedom.