As'salamu Alaikum akhi Ramihs,

Here are my responses to your points above:



Noble Verse 51:48:

1-  ‏51:48 والارض فرشناها فنعم الماهدون

FARASHNAHA فرشناها is derived from FARASHA فرش, which means:

1.  To spread out.
2.  To clothe.  As in farasha al-sareer (placing the cover on the bed).  Farasha al-sareer also means prepared the bed, as in made it neat and ready.

الماهدون MAAHIDOON is derived from MAHD, which means:

1.  Make comfortable.
2.  Cradle.  As in from cradle to grave (Mina al-madh المهد ila al-lahd لحد).

So basically earth is a PREPARED BED for us.  But this bed is also a rocking one as Allah Almighty Said in:

78:6 الم نجعل الارض مهادا

[078:006] Have We not made the earth as a wide expanse rocking cradle  مهادا,

Notice the following:

  

مهد means bed.

مهادا means a rocking bed.

  

The relationship and balance between مهد and مهادا in Arabic is like:

1-  حرث (harth), tilth, and حراث (hiraath), plowing the earth.

2-  قتل (qatl), kill, and قتال (qitaal), fighting.

3-  جهد (juhd), effort, and جهاد (jihaad), struggling. 

So مهد is bed.  مهادا is a bed in action.


Let us now look at our planet earth's "Axial Tilt" that makes it look like a cradle:



www.answering-christianity.com/detailed_meanings_of_scientific_words_in_verses.htm#geology_moving_earth_rain




Noble Verse 84:3:

This is a future Prophecy regarding the streching of earth that had been scientifically confirmed.  It is a STUNNING one and I have written an article on it with detailed Western scientific references and also videos proving this:

www.answering-christianity.com/end_of_times_volcanoes_caused_by_stretching_of_earth.htm




Noble Verse 21:44:

There are two scientifically proven answers for this Noble Verse:

1-  The actual planet earth is shrinking.  This had been confirmed by NASA and other Scientific agencies:

www.google.com/#q=earth+is+shrinking


2-  The rising seas (a Quranic Prophecy) are reducing the livable lands that we live on.  Entire towns will drowned by the sea:

www.google.com/#q=sea+levels+are+rising

The rising seas before the Hour is an End-of-Times Prophecy in the Glorious Quran;

[052:001]  By the Mount (of Revelation);
[052:002]  By a Decree inscribed
[052:003]  In a Scroll unfolded;
[052:004]  By the much-frequented Fane;
[052:005]  By the Canopy Raised High;
[052:006] And by the Ocean filled with Swell;-
[052:007]  Verily, the Doom of thy Lord will indeed come to pass;-
[052:008]  There is none can avert it;-
[052:009]  On the Day when the firmament will be in dreadful commotion.
[052:010]  And the mountains will fly hither and thither.
[052:011]  Then woe that Day to those that treat (Truth) as Falsehood;-

‏52:1 والطور
‏52:2 وكتاب مسطور
‏52:3 في رق منشور
‏52:4 والبيت المعمور
‏52:5 والسقف المرفوع
‏52:6 والبحر المسجور
‏52:7 ان عذاب ربك لواقع
‏52:8 ماله من دافع
‏52:9 يوم تمور السماء مورا
‏52:10 وتسير الجبال سيرا
‏52:11 فويل يومئذ للمكذبين

By the way, the atmosphere being our raised and protective roof is also mentioned in several Noble Verses in the Glorious Quran:

www.answering-christianity.com/ozone_layer_protecting_earth.htm


As to "sides", the spherical earth does still have boundaries.  Lands on earth are divided into sections.  Perhaps this is even referring to the continents after they broke off from each others as the earth expanded:

‏13:4 وفي الارض قطع متجاورات وجنات من اعناب وزرع ونخيل صنوان وغير صنوان يسقى بماء واحد ونفضل بعضها على بعض في الاكل ان في ذلك لايات لقوم يعقلون

[013:004] And in the earth are neighbouring tracts وفي الارض قطع متجاورات, and gardens of vines, and green crops (fields etc.), and date-palms, growing out two or three from a single stem root, or otherwise (one stem root for every palm ), watered with the same water, yet some of them We make more excellent than others to eat. Verily, in these things, there are Ayat (proofs, evidences, lessons, signs) for the people who understand.



This is explained in more details in the following sub-section.