There's only one level-based bump so far. If it started as 17, then up to 18 at level 4, and a +2 Int item, it could be 20, but I skimmed your items and didn't see a Headband of Intellect on there.
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I wrote up a quick overview of Sindre's background. It's on my sheet, but here as well just for reference:
Sindre was born in Zilargo, as many gnomes are, but the circumstances of his younger years remain a mystery. He spent much of his time traveling, primarily in research of ancient arcane tomes and curios. His journeys brought him everywhere from Sharn to Stormreach (as well as further into the depths of Xendrik), and some say even to the outlying planes as well.
It was recently that Sindre was contacted about some business in Sharn, rather mysteriously at that, which brought him to the city not long prior to the catastrophe. Now that Sharn has fallen, it stands to Sindre to find out what events conspired to bring him to the City of Towers on this momentous occasion.
tl;dr - Born in Zilargo, travels a lot, mysterious dealings, etc.