Ms Chavez, I'm sorry to say I that I have to agree, for the most part, with earlier comments. I am sympathetic to offense you have taken to statements made by Richwine in his earlier work (although based on the Heritage statement in response I am inclined to give him the benefit of the doubt until I learn more). But his earlier work, as a student and research assistant, doesn't change what this paper says or the methodology it employs. I think you should return to the Heritage site and re-read their current report.
The criticism you write today seems more about the earlier Richwine paper. Whether it is justified or not, it is irrelevant as criticism of this latest Heritage paper. All the "browning of America" commentary may be obnoxious to the extent it amounts to ethnic or racial stereotyping. But Heritage, in analyzing based on census data by country of origin does nothing like what you allege. Res ipsa loquitur.
As far as the static versus dynamic modeling, there is a concept known as "sunk cost." If you project far enough into the future you may find that even those descended from illegals will be a net plus in terms of tax revenue. But in the early years it is impossible that they won't cost something. To the extent that they use any government programs without having been here long enough to fund them, they will be a drain on revenue.