It is a strange case. You say that the author of the two papers is deceased. Given that and the other facts you have presented -- in particular both papers were published almost ten years ago, their flaws would be immediately suspected by any mathematician and are documented in the MathSciNet reviews -- it seems to me that the principal culprit and the principal victim are both the International Journal of Mathematical Education in Science and Technology (IJMEST).
The journal in question is apparently reputable (otherwise I would not bother)
Is it reputable, though? I hadn't heard of it before. Taking a look now, it is hard for me to tell.
and is published by a major commercial academic publisher,
Come now: we all know that being published by a major commercial academic publisher is no certificate of quality. Elsevier was caught publishing a several journals that were essentially reprinted advertisements for medical and pharmaceutical companies. That's memorably egregious, but other big companies have skullduggeries of their own. Conversely, big companies which do some really shady things also put out some really good journals, Elsevier being a good example. Taylor and Francis is a less good example: of the 46 journals they publish in mathematics and statistics, I only myself recognize three as being good...but three is enough. So major publishing companies publish good journals and bad journals: I don't think one can deduce much from this.
Back to the journal. I looked into IJMEST, and I find it a bit strange. The journal's aims and scope center it on (a kind of) mathematics and science education:
Contributions will be welcomed from lecturers, teachers and users of mathematics at all levels on the contents of syllabuses and methods of presentation. Increasing use of technology is being made in the teaching, learning, assessment and presentation of mathematics today; original and interesting contributions in this rapidly developing area will be especially welcome. Mathematical models arising from real situations, the use of computers, new teaching aids and techniques also form an important feature. Discussion will be encouraged on methods of widening applications throughout science and technology. The need for communication between teacher and user will be emphasized and reports of relevant conferences and meetings will be included.
I wanted to remark that I have a colleague who is (to say the least) active in the mathematics education field, so I know that the above description is not really that of a modern research journal in mathematics / science education. It is more along the lines of creating a shared community for mathematical teachers (which is also a worthy goal, and one that my colleague is interested in).
But the above description does not seem to be a good match for the papers in which IJMEST has published in recent years. These papers seem to be almost entirely in the field of mathematics itself: most papers state theorems and give proofs. Sometimes they knowingly give proofs of old theorems and their angle is to give new proofs, often accompanied by the claim that they will be easier for the student to understand (although in my experience as a mathematician it is common for new proofs to be accompanied by such claims). But many, perhaps a majority, of the articles, seem to be entirely devoted to mathematics, usually of the kind that is broadly understandable: e.g. lots of Fibonacci numbers. So the published work of the journal looks to be a lot closer to what is published by the Mathematical Association of America (MAA)...but without nearly as much attention to the quality of the exposition as given by articles published in MAA journals.
So something has gone terribly wrong for this journal to publish proofs of major open problems like Collatz or Goldbach: such papers should be out of scope of the journal. As @Corvus points out, submitting a paper claiming a proof of something like Goldbach to a journal like this just doesn't make any sense: such a paper should be published not only in a math journal but in one of the very top math journals, first because a correct proof of Goldbach merits publication there (such a proof would rank among the great mathematical achievements of all time!) and second because a top journal can get the top experts in the field to the vet the paper, which is needed in order for the community to accept the result.
When the editorial board of a journal like IJMEST receives a paper claiming a proof of a major conjecture, they should (I think) do one of the following things:
(i) Bounce the paper back immediately as being out of scope for the journal, or
(ii) Engage in a preliminary refereeing job to see if the paper looks serious. If so, they should reach out to the editorial board at an appropriate journal -- i.e., a top mathematics journal -- and try to do a handover of some kind.
I've thought it over for a while now (slow internet connection...), and although in general I believe strongly that any interested party can contact editors and try to get published results corrected, in this case I just don't see why that would be a helpful thing to do. I realize that I now believe that publishing short, fallacious proofs of two major conjectures in the same year is enough to irreparably damage the reputability of a mathematics education journal in my eyes. Either they are so far outside of the mathematical community that they don't understand the significance of problems like Goldbach to the mathematical community and how they have to be handled or they know and don't care: in particular, they don't really care whether the mathematics they publish is correct. I don't see how to fix either of those problems.