at 51 I doubt any natural methods are going to work.

The 2000ng wont help him develop more muscle but if it is the sublingual spray hell notice some tighter skin/darker hair/bf loss in around 6 months to a year with it.

Nothing incredible but hell notice it.

The 6oxo will give him an increase in testosterone but I doubt itll get noticeable mass on him. Plus itll drive estrogen lower then where it needs to be most likely. Id reccomend DIM for him as itll keep his estrogen within range without being too low.