Because of the leading $ (which is text on the clipboard, not a number format) the numbers copied from your browser have been pasted as text. You can see this because all the “numbers” are aligned to the left. If you click on the $45.00 you will see '$45.00
Easily fixed, just select your column of numbers, click Data > Text to Columns and click OK. Your text “numbers” should then become real numbers formatted as currency and your sum should return a total
It looks as if you have a theme installed. Removing the theme, or possibly changing to another theme, should fix the tooltip. Settings are in Tools > Options > LibreOffice > Personalisation. I don’t know how to change colour of tooltip itself. Cheers, Al