Please help - why can I not take crisp interior photos

Hello Everyone,


I have been into photography on an amateur basis, I am now getting more into interior photography but wonder why my pictures do not pop. I have attached some pictures of real estate taken by others and I would just like to take similar shots.

My camera is due for an upgrade, but I am sure its not about the camera, its about how I get the best out of it.

I have a Canon Rebel 5, a 430Ex, 4 x lens, wide angle Sigma lens, Tamron lens and a portrait lens. The 430 ex can be mounted off camera and remote trigger. I read a lot before taking shots but when I start to take the shots it doesnt come out and I am often left disappointed. I have some basic questions please.

Shoot manual or specific mode.
I do not shoot in direct sunlight but what is the safe setting to use in most cases, I try f8 and always use a tripod
Light on or light off ?
How can I capture outside the window without washing it out, I understand HDR is the way, when I take HDR shots and shoot with the aperture 3 steps down, and 3 steps up, then merge. It doesnt come out right.
I only use Lightroom and my photo editing skills are basic.
How do I keep my shots in focus, the tail end of it tends to blur out. This is why I started using F8 to keep it all in focus.



[Mod edit: images not owned by OP converted to links]

The subject matter is very filled with white, with few contrasting elements in them. There is little a photographer can do with such a subject. You could create a differential of brightness 'close to cameral' vs. 'far from camera' via supplemental lighting, to increase the sense of depth, for example.
What traditional photographers did in the days of film for the view outside the window would entail a lot of work to simply reduce the differentail of brightness between indoor vs. outdoor view seen thru window

• light the interior to be brighter like outdoors
  
• filter the windows to be dimmer scene coming thru the windows
  
• shoot at a time when outdoors was simply a lot darker than prime daylight hours
  

The attached photos were created by technique known as "flambient" (flash-ambient). It is a technique where you take at least two photos with completely different exposures, one for the interior and another for the exterior, which must be taken with a strong flash. Then, in Photoshop, you overlay the flash photo onto the ambient photo and locally brush over windows and other overexposed objects in the first photo using the "darken" blend mode to achieve a perfectly exposed interior and exterior. To achieve the colors in the final image, you can use the flash photo as an additional layer for the "color" blend mode.

How can I take similar photos with my existing kit, any tips ?