Let’s take a close look at Sentence 1: “Erikson’s theory goes a long way to
explaining why too much of anything is not helpful for developing a well balanced personality.” It is grammatically flawed because of its misuse of the preposition “to.” This makes it needless or impossible to determine whether the word “explaining” in that sentence is acting as a verb or as an infinitive.
However, we can correct that sentence by replacing the preposition “to” with “in.” The sentence will then read as follows: “Erikson’s theory goes a long way
in explaining why too much of anything is not helpful for developing a well balanced personality.” This way, we have produced the gerund phrase “explaining why too much of anything is not helpful for developing a well balanced personality” as the object of the preposition “in.” Here, of course, the gerund phrase—an extended form of the gerund “explaining”—acts as a noun and not as a verb.
Alternatively, we can correct Sentence 1 by replacing the word “explaining” with “explain,” making the sentence read as follows: “Erikson’s theory goes a long way
to explain why too much of anything is not helpful for developing a well balanced personality.” In this construction, we have produced the infinitive “to produce” in the extended infinitive phrase “to explain why too much of anything is not helpful for developing a well balanced personality.” This extended infinitive phrase acts as an adverbial noun phrase modifying the verb phrase “goes a long way.”
Now let’s take a look at Sentence 2: “Many parents say that their sons have gotten to
watching TV only on weekends and at most an hour on weekdays.” This is a grammatically airtight sentence where the gerund phrase “watching TV only on weekends and at most an hour on weekdays” acts as the object of the preposition “to.” As such, that gerund phrase acts as a noun and not as a verb; it “receives” the action of the verb intransitive verb phrase “have gotten” through the preposition “to.” (Recall that intransitive verbs can’t have a direct object and can only act on it through a preposition as an “intermediary” mechanism.)
As to your other question, the word “explaining” in the first sentence you presented as well as the word “watching” in the second sentence you presented are not in the present tense—in fact, they can’t take any tense at all—because they are not functioning as verbs. They have become
verbals, which are words that combine characteristics of a verb with those of a noun (infinitives, gerunds) or of an adjective (participles). Verbals are the so-called
non-finite verbs, a form that has no duration and cannot take tense, as opposed to the so-called
finite verbs, the regular verb form that has duration and can take tense.
For a much clearer picture of how verbals work in contrast to regular verbs, I suggest that you study the readings that I have listed below.
RELATED READINGS IN THE FORUM:Can intransitive verbs take a gerund or infinitive phrase as direct object?How finite verbs differ from non-finite verbs