Late on the scene but have had similar stubborn glue spot issues on my blue flame top Tele.
WARNING: Be very, very delicate and careful when using brass 'toothbrush' or even a regular toothbrush as it is so easy to dig deep scratches into the veneer whilst trying to remove glue spots as I found out the hard way. Thankfully I didn't go through the veneer to surface underneath but there were noticeable gouge marks that were filled with saturated layers of Tru Oil in those parts. Not ideal but solved most of that problem.
Best thing is to be patient with using Goof Off which smells like an Acetone based solvent. Powerful stuff as it even ate through the blue Nitrex rubber gloves I was using at the time. Remember to use a clean white cotton lint free rag or cloth so that you don't transfer any dye colour from the rag to the guitar body. You may need to have several attempts at it to get most of the stubborn bits off and as Dedman said, sometimes you can only do so much and then have to figure out how to disguise the remaining bits. Solid paint or permanent marking pens are the only ideas that come to mind.
Also reckon you have enough black in the mix and need to add more red as the Tung Oil will darken things up a bit too.
Edit: Centreline looks pretty tricky and may need a very steady hand to scrape some of the glue out of the join and then load up with lots of red stain. As you add top coats leave body lying face up and be careful not to create runs or puddles around what you are trying to hide and fix. It will probably take many coats, possibly 8-10 before things level out and suggest a very light sand with 1200 or finer wet & dry used wet after about the sixth coat. If done before there may not be enough thickness in the coats to handle any sanding. Do not recommend using steel wool at all as it can lead to other problems that are even harder to fix.
The red ink looks like stamp pad ink and wonder if you have tried mixing a bit of the fountain pen ink with it as that should give a more vibrant shade of red to crimson?
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