Re: Obligatory Prayers : 3 or 5 ?
In my reading, Quran-only followers interperet it as only 3 prayers, those that follow hadith interpret it as 5. It is not the easiest verse to understand, for sure.
All other Quranic proofs point to 3. I think the better argument would be for you to just say "we follow Muhammad's example" since you apparently don't have any issue with Muhammad receiving revelations from Allah outside of what was revealed in the Quran. That will cover most all of your bases on practicing things as part of Islam that weren't actually God's (protected) words from the Quran.
But I think since most Muslims believe God created us soley to worsihp him would agree that either number is a minimum.
Peace Seminole
Just to make things easier for all to view here are the references for prayer in the Qur'an:
11:114 Two ends of day and in the night (IS)
17:78-9 From Midday Until Darkness, recite in dawn, parts of night (IS)
20:130 Before rising sun, before setting, during some of night, and ends of day (SH)
30:17-8 Come up to evening, when enter the morning, in afternoon, when day begins to decline (S)
50:39-40 before rising of sun, before setting, during part of night (SH)
52:48-9 when get up, night time, at star set (SH)
73:1-6 most of night, just less than half of night, or just more (Q)
73:20 <2/3, 1/2 night, 1/3 of night (Q)
The terms IqamasSalah (IS), Sabbih Hamdih (SH) and Qoomi (Q), translate to, perform Salah, Glorify/Praises and Stand. These three terms in the above context are identical. To support this, the way the instructions are phrased are the same, such as two ends of the day is reflected in an (IS) ayat as well as an (SH) ayat. The same goes with the (Q) ayats.
Also, note that the verses 17:78 to 79 refer to a duration rather than specific times. From Midday Until Darkness. This obviously indicates are range of praying times, it cannot be limited to two. In fact, the Qur'an speaks of 6 prayer times, including Tahujjud - Deep night optional prayer.
Now, going by the tone of your post, you would like me to admit that the Qur'an does not require 5 prayers. And that Muhammad (SAW) had sanctioned 5 due to extra Qur'anic revelation. I believe in extra Qur'an revelation, but I do not agree with your assertion about 5 not being in the Qur'an. The term Hamdih means Praises and this translates to mainly Surah Fatihah which is an obligatory part of Salah. None of the above verses can really be selected in isolation for those who understand Islam from the insiders viewpoint.
I also think it unfair that you have tried to suggest there are ALL other Qur'anic proofs when there are only two verses which specifically refer to (IS) and times, all other verses are either (Q) or (SH) type. Then we have muttawatir hadith which categorically show how the Qur'an should be understood. Of course not being a Muslim and attempting to find discord in the Qur'an as suggested by your topic name, you have been thrown off course by the Qur'an. None of these verse LIMIT the number of prayers to either 5 or 3 so the question in the topic has been redundant from the beginning.
Though I find your approach more humourous than others here, you seem to have found yourself a fan, because you artfully have found a way to both be unfairly dismissive of Islam at the same time as being an authority on it, complete with understanding and opinion. LOL