all this assumes he was not covered under your Marketplace Health Insurance. what may be happening. including him as a dependent requires that his modified AGI be included in household income unless he is not required to file a return but filing only to claim a refund of withheld income tax or estimated tax. Otherwise, including his income would likely lower the subsidy you were entitled to vs what you got.
What we don't know because we have no data is the effect of including him vs not. there may be loss of various tax credits that would more than offset any increase in repayment of the health care subsidy. if you are not married, then without another dependent your filing status would be single vs head of household which would also increase your taxes.
the only way to tell which is best is to do 2 computations. one including him and then one that does not. then compare lines 34 and 37
if both show an amount on line 34 it would likely be best choosing the one with the larger refund
if both show an amount on line 37 it would likely be best choosing the one with the smallest amount due
if one has an amount on line 34 and the other on line 37 it would be best choosing the one with an amount on line 34
now if your son was covered under your Marketplace policy, there are numerous possibilities because of the very liberal rules for allocating policy amounts. in addition, your son would have to file a return,
