the product that he could dismiss the question of "expressing feeling in written words" as the merest trick of the literate

So intent was he on showing the perfect compatibility of the stereotype and the product that he could dismiss the question of "expressing feeling in written words" as the merest trick of the literate.

Ludlow's strong drive in his goal to show the compatibility of the stereotype and the product was the reason in his deciding that the problem of "expressing feeling in words" was insignificant as he made it to be no more than a question of using the slightest artifices available to people knowledgeable in literature.

A first addition prompted by this comment by user Purfecr: "I think your reply just added to the confusion. Could you write in a simpler style? I'm not that good at English.".

I am sorry to say that you are not going to explain anything complicated with only basic vocabulary and embryonic concepts, unless you give your explanations great length so as to define everything from simple parts. I did what I could here to identify more relevant concepts than in the above but you will be left to your own device in the way of clarifying the meaning of certain terms, particularly grammatical ones.

The construction "So … that" is a correlative subordinator (CGEL, 14.13), the subordinate clause being "that he could … of the literate". It is a subordinator that introduces a clause of result (CGEL, 15.74). It introduces "constructions that combine the notion of sufficiency or excess with the notion of result". "The adverb 'so' premodifies an adjective or adverb." Here the adjective "intent" is premodified by "so". ("to be intent on something" means "to give all one's attention to sth".) The correlative "that" is sometimes omitted. Here are now simple examples that show the relation.

• I'm so happy to hear your good new that I could kiss you. (CGEL)
  (The intensity of the happiness felt is sufficient for justifying kissing; in other word, the happiness being great enough, it could result in a kiss (or kisses).)
• So few people came to the meeting that it was adjourned. (CGEL)
  (The number of people was really little and it followed from that that the meeting was adjourned; the number of people was low enough and a result of that was adjournment.)

We can now apply that to the sentence.

So intent was he on showing the perfect compatibility of the stereotype and the product
that he could dismiss the question of "expressing feeling in written words" as the merest trick of the literate.

Main clause

"So intent was he" is a construction in which the predicative expression (in other words, the copular complement "so intent") is fronted (for emphasis). The sentence is equivalent to "He was so intent on…". Ludlow was giving a great amount of attention to showing something (ie. compatibility of stereotype and product) and it was great enough to produce the result that is expressed in the that-clause. In other words, he had such a strong incentive to achieve his goal that he went to the extent of doing what is explained in the that-clause.

Subordinate

The verb "to dismiss" can be used without a complement or—that is often the case—it can be used with a complement introduced by "as", as is the case in this subordinate. What this adverb signifies here is "reason"; instead of "as" you could have read "in reason of it being", however not without a stronger nuance of the reason being status quo; I say "nuance" because it is still possible to doubt that what is being related is reality instead of reality as the speaker would have it. Indeed, we do not know from the text whether the reason should be a contention of Ludlow's or a widely recognized fact, although we may presume the former.
This reason, then, whether allegation or general knowledge is that the question of the expression of feeling comes down to something rather insignificant (the merest), nothing else than an artifice (a trick), moreover, something which as a means, is available to the literate (understated: as a whole; and we have to assume here the literate of both sexes).