DISCLAIMER: This puzzle is wrong! There are numbers who are wrongly calculated. I will try to make another one which will (hopefully) be correct. Thanks to @TheNoah for the correction. Every clue is a number and when converted into roman numerals you get the answer
Clever! Tricky figuring out where to use "improper" Roman numerals, to make the across and downs work together. Like, 2100 would normally be MMC, but making it work with the across entries requires it to be MDDC. Fun little twist.