What would have been the price of a loaf of bread in 1645 Amsterdam?

According to this database (specifically the spreadsheet file, column D) a 100kg of rye bread cost 8.22 guilder in the western Netherlands in 1645, which should at least give you a rough idea to start with. (Here is the same spreadsheet shared on Google Docs for convenience). Using @JustCal's suggestion of 3lb per loaf, this works out to roughly 0.1 guilder per loaf.

I think your best bet for more info is to look at the work of Jan de Vries, for example the article "Taxing the Staff of Life: The Dutch bread tax, 1574-1855" and the book The Price of Bread: Regulating the Market in the Dutch Republic.

EDIT: Regarding wages, this page on "Money in the 17th century Netherlands" claims, "An outdoor laborer earned 6.50 guilders per week... A master carpenter earned 9 guilders per week... Wages did not change for 150 years." I am fairly certain de Vries has more data on wages and I will update if I can track this down.

I don't think you're going to find anything close to the precision you are asking for here. And as DevSolar has commented I think you are way off the mark by specifying prices in gold.

I do have one example for you though: In his Autobiography Benjamin Franklin recounts his journey as a young man in 1723 from Boston to Philadelphia by way of New York (and accidentally Brooklyn). He has walked, rowed, sailed etc for days and days. He famously accounts his arrival in Philadelphia as follows (emphasis mine):

I was very hungry; and my whole stock of cash consisted of a Dutch dollar, and about a shilling in copper. The latter I gave the people of the boat for my passage, who at first refus'd it, on account of my rowing; but I insisted on their taking it. A man being sometimes more generous when he has but a little money than when he has plenty, perhaps thro' fear of being thought to have but little.

Then I walked up the street, gazing about till near the market-house I met a boy with bread. I had made many a meal on bread, and, inquiring where he got it, I went immediately to the baker's he directed me to, in Second-street, and ask'd for bisket, intending such as we had in Boston; but they, it seems, were not made in Philadelphia. Then I asked for a three-penny loaf, and was told they had none such. So not considering or knowing the difference of money, and the greater cheapness nor the names of his bread, I bade him give me three-penny worth of any sort. He gave me, accordingly, three great puffy rolls. I was surpris'd at the quantity, but took it, and, having no room in my pockets, walk'd off with a roll under each arm, and eating the other. Thus I went up Market-street as far as Fourth-street, passing by the door of Mr. Read, my future wife's father; when she, standing at the door, saw me, and thought I made, as I certainly did, a most awkward, ridiculous appearance. Then I turned and went down Chestnut-street and part of Walnut-street, eating my roll all the way, and, coming round, found myself again at Market-street wharf, near the boat I came in, to which I went for a draught of the river water; and, being filled with one of my rolls, gave the other two to a woman and her child that came down the river in the boat with us, and were waiting to go farther.

Philadelphia in 1723 is not Amsterdam in 1645 but you get the general idea... (at least we are near a harbour): bread is sold by the penny not the gold piece.

Some things to note:

The price of bread in Philadelphia is substantially lower (3x?) than in his native Boston.

The types of bread offered in the two places is different, this may make your comparisons difficult even if you find the data.