How do the Sola Scrptura folks react to the Dead Sea Scrolls and other more recent discoveries of ancient Biblical texts not among those canonized by Martin Luther?

Actually, Luther was influenced by the books of the Masoretic Tanakh and did, originally, include the Apocrypha.

Even Jesus questioned how the Messiah was David's son.

Nuda Scriptira is scripture alone. Sola Scriptura is writings authority over traditions and does not imply Biblical inerrancy (see above in regards to Jesus, and genealogy to David).

Can we trust the Bible when Constantine and the First Council of Nicaea took out many books of the Bible and altered existing translation by removing things?

If you study, you will find passages in the Orthodox Bible, not in the Catholic.

In response to A2A:

Just as there are a few discrepancies between the Masoretic and Samaritan Torahs.

Was Jesus Christ Jewish?

Since the Bible is a collection of writings (literally what biblia means), you will even find that while Matthew and Luke have genealogies, Paul wrote to Titus and Timothy not to pursue foolish genealogies.

The influence of the Christian Old Testament was the Septuagint, which predates Jesus. Luther, also maintained the Septuagint philosophy of law, history, poetry and prophets, in ordering, while the Tanakh followed Torah, prophets (Nevi'im) and writings (Ketuvim).

However, if one is using the Bible as a premise and traditions, how does one evaluate discrepancies between the two, as traditions are interpretations of Bible passages as their claim for validation.

What’s wrong with anti-imperialism?

The New Testament was established as part of creating a universal (catholic) interpretation for all Christians.