I searched that site. Home page is at www.chompchom.com
I don't see those numbered rules listed anywhere. There are "comma rules", but only 7 of them.
Most of the advice seems good, but of the three examples he gave for "lonely verb", two also start with a coordinating conjunction ("but","and") which he ignored in the fix. The third semtence there is a cleaner example of "lonely verb". The essence of a lonely verb is that it has no noun or noun phrase acting as a SUBJECT. What you choose to insert as a subject is up to you, if you have no other context (sentence before or after the faulty one.)
As for infinitive phrases, just remember that an infinitive does not count as a sentence verb (likewise for participles and gerunds). A sentence needs to have a conjugated verb that matches the subject. (In the prior sentence, "needs" is conjugated to match "sentence"; without it, "Sentence to have..." does not make a sentence.)
I do not know good sources to recommend. But I applaud your effort to learn these aspects of sentence construction. Sadly, many native speakers never learn them well enough, and end up writing incomplete, confusing sentences!