At the rate senior DFEs are leaving (upgrade, base transfers etc) it could be over a year from date of hire before you get even a bad line of flying in Dallas on the 145, unless something changes for the better - nothing ever does.

I think the best way to see DFW would be to quit and go elsewhere or ride out your first year in LGA and enjoy it for your second or third year as an FO before you finally get your hours, by then you’ll be a year behind the 175 guys upgrading and can probably snag a DCL seat if you want it.