Dear Bob,  I concur with your assessment of John Phillip's solution
to keep the dowel heads from traveling or shifting.  Burnt shellac is
good.

There is a product called I think 'Swell-Wood', it is generally used
in wood to wood applications where you wouldn't want to glue say a wood
dowel into a lower chair cross-member.  The product is applied to the
raw wood surfaces, then the pieces are pressed together and then
allowed to set while the wood parts swell to create a tight joint.
(This is only a suggestion, as I do not know all of the recommended
applications of the product mentioned, or whether it would be
corrosive to metal.)

Another possible alternative is to find out what the composition of the
paint/fixative that is used in electronic devices to prevent screws
and/or nuts from coming loose within the components.  (If they did fall
away and land upon a circuit board ... well, you know the rest!).

Or an extremely labor intensive method of removing each and everyone
of the dowel-heads, screwing a leather nut down the pushrod, then
replacing the dowel-head, make your height adjustments, and then
tightening the leather nut and dowel-head against one another -- voila!

Now on to the problem with removal of the Gorilla Snot/Glue.  I think
it is safe to say that if a company is going to place a product on the
market, it would be in their best interest to make sure there is a
solvent to undo it's miraculous holding properties.  Try looking them
up on-line, and inquire whether they offer a thinning-agent/remover.

Hope some of this helps.

Sincerely,
D.F. Rowe
Bronx, New York, USA