On your 1st question, I would say generally about +/- 20% from the center of the recommended range is about all you should go. The higher the compliance, the more careful you have to be about adding force. If you have to go very far out of the recommended range, then there is likely something wrong somewhere.
On the 2nd question, you are overdoing the concern about absolute level of the tonearm, regarding VTA adjustment. All you have to do is look at it from the side while it is playing. The level is simply a starting point, from which you make your final adjustments by ear. Get it where it looks level by eye, and listen to a record. Then make adjustments according to the frequency balance. Typically lowering the VTA will shift the balance toward the bass, and raising it will shift it toward the highs. Fine tuning within this range will allow you to adjust out sibilance and other artifacts that might be present.
Question 3. What kind of TT, arm, and cart do you have? If you are out of adjustment range, then you may have some other conditions we need to know. Even to recommend a mat, we need to know more.
Question 4. Alot of folks use the HFN&RR test record. I don't use any test record, except my collection.
On the 2nd question, you are overdoing the concern about absolute level of the tonearm, regarding VTA adjustment. All you have to do is look at it from the side while it is playing. The level is simply a starting point, from which you make your final adjustments by ear. Get it where it looks level by eye, and listen to a record. Then make adjustments according to the frequency balance. Typically lowering the VTA will shift the balance toward the bass, and raising it will shift it toward the highs. Fine tuning within this range will allow you to adjust out sibilance and other artifacts that might be present.
Question 3. What kind of TT, arm, and cart do you have? If you are out of adjustment range, then you may have some other conditions we need to know. Even to recommend a mat, we need to know more.
Question 4. Alot of folks use the HFN&RR test record. I don't use any test record, except my collection.