The statement that he cannot get enough nutrients via blended "real food" is ludicrous, considering that's what most living people eat. Liquid vitamins and supplements are also widely available if needed. Of course, you follow food by flushing fresh water through the tube.
A
recent study found no clogs in PALS using blenderized diets, and although I think
this paper is overblown in terms of process, it makes the points that blenderized tube diets are widely used and well tolerated (and their use is growing as people realize the distance between commercial formulae and real food that got them this far).
As Tillie said, there are online groups everywhere, including the Oley Foundation, many of them parents of children who are still growing, who will testify that the nutritional concerns are bogus if you think about nutrition just as you normally would and because ALS is a disease of hypermetabolism, don't spare good fats and proteins. Meat can be pureed. Eggs, nut butters, non-dairy milks if he is sensitive to dairy, canned fruit, are just a few examples. Search on home enteral nutrition and blenderized tube feeding.
It really doesn't matter what the doctors think, but if you want to educate them, you can send them these URLs and suggest a brief search in PubMed -- I couldn't possibly list all the papers. You can also find a registered dietician experienced with real food tube feeding if you want that support, but the concerns I saw in the literature around nutrition (and likewise concerns about contamination, which are pretty silly as
this paper shows unless your kitchen is a cesspool) were essentially low-quality meta-analyses, driven more out of fear of change and perhaps industry grants than an evidence base.
I put the burden of proof in the other direction, so long as you adapt your recipes to his own tolerance, energy and weight. This is an N of 1 enterprise, just as what you thrive on was never what your next-door neighbor does.
Couple of papers showing weight gain/improved tolerance on BTF when switched from commercial formulae:
BTF effectively mitigated weight loss, GI symptoms, QOL scores, and total energy intake in this group of patients with HNC who received tube feeding for 6 weeks.
pubmed.ncbi.nlm.nih.gov
BTF was found to be safe and effective in promoting weight gain in adult participants who required HEN for at least 6 weeks.
pubmed.ncbi.nlm.nih.gov
Hope this helps.