Guy gave you the unfortunate truth of the situation. There is a Jacob Young under every leaf of cabbage it seems, but period documentation of the gunsmith as such is either rare or possibly non-existent.
Regarding your Jacob Young, it is a possibility, but unlikely. Is he documented as a gunsmith? If so, he may either be the one, or -- my guess -- he may be related to the Youngs who worked around Hampshire Co. Va. (WVa.), who may be related at some distance, although that is speculation.
The Whitley rifle was made NO LATER than 1813 and likely somewhat or even much earlier than that, because that is the year Whitely died in the battle of Moraviantown (Ont., Ca.) carrying that rifle. It is unlikely but not impossible that a 23 year old (at most) was selected to make that rifle.
If you have any information on the JY born in 1790, such as his parents, wife, etc., it might be helpful and fit into what little we can speculate about the "real Jacob Young" or to relate him to others. There is a lot I would rather not go into, as the waters are muddy enough. On the other hand, even unlikely possibilities need to be examined.