Gumby, God and Jacob, in case you haven't heard, suffered from short-term memory loss.
Actually the first name repetition on God's part is evidently simply to confirm the change. Similar examples appear when comparing Gen 21:31 with 26:33 (where Beersheba is apparently named twice, though by different people - Abraham and then Isaac) and again when comparing 28:19 with 35:15 (where Bethel is twice named, both times by Jacob). Also, God reiterated his promise to Abraham on several occasions. Again, short-term memory loss seems like a good explanation, though I'd imagine that these examples might illustrate a literary feature of the book, since Genesis features several different literary devices. It's also God's way, apparently, of emphasizing that he will indeed carry out what he speaks.
As for Genesis 32:30, the common explanation is that Jacob actually wrestled with an angel, and simply used the term God interchangeably, as he did in 48:15 (referring to God as "the Angel who has delivered me from all harm"). Manoah, as recorded at Judges 13, also saw an angel and yet exclaimed in verse 22 "We are doomed to die...We have seen God". Back in Genesis 18, Abraham is having a discussion with one of the three angels that came to him, after two of them departed to Sodom, and refers to the remaining angel by the divine name.
You can buy all that, or simply accept short-term memory loss as the real reason. Sometimes, I'm tempted to do that - it makes such things seem much clearer.