"He did not pay himself a salary. " Good; partners cannot have salary.

"This could be treated as a guaranteed payment." Possibly, since Partner Son is working and that is how a working partner gets paid. Guaranteed payments are deducted from net income and are part of total loss of $30,000.

"The partnership agreement states that the son owns 49% of the partnership and the dad owns 51%. It doesn't mention anything about who contributed what and that any profits or losses will be divided according to the ownership percentage. " How does it says ownership is 49/51 but doesn't say contributions or profits and losses?

"The dad contributed around 150K during the year to get it up and running. He did not do any of the work." Was this money contributions or loans?

Call the partners and their lawyer for more info.