1. This switch may not be as abrupt as it seems at first to us. As we shall see in the summary below, the psalm seems to recall the exodus in subtle ways. In Psm 78:19, the psalmist recalls the rebellion of the people during their time in the wilderness and he says, "they spoke against God, saying, 'Can God spread a table in the desert?'" The poets of ancient Israel seem, therefore, to see very different possibilities from our imagination of what God as the shepherd of His people can do.
2. The verb 'anoint' dashen used here is to be distinguished from mashach from which the noun "messiah" is derived. The noun deshen refers to the fat or the ashes from the sacrificial animals. Since fat animals are considered the healthiest and the fat regarded as the best part of the sacrificial animal, the word came to be associated metaphorically with prosperity and richness. To "anoint my head with oil" in this verse should, therefore, be understood as a symbolic gesture of blessing the psalmist.
3. What is translated as a verb "overflows" or "runs over" is, in the Hebrew, a noun, rewayah, which is literally, "saturation." The line is, literally, "you have prospered my cup with saturation." "My cup overflows" is a good translation; "Intoxicated" is a possible translation in some context (cf. Samuel Terrien below) but probably not here.
4. On "not 'runneth over,' but 'is intoxicated'," see Note 3 above.
5. Lot is often preached as a faithless fakeless person. For more on him, see Lot.