First of all, Shabaash to you for doing the effort of writing Guru Sahib's Amritmai Gurbani. Doing paath of Gurbani, doing Kirtan of Gurbani, Writing Gurbani and doing Vichaar of Gurbani are all part of Gurmat Bibek that we all should strive to do.
Quote
1) when having mahala followed by number, should the number be separeted like "m 5" or connected "mahala5".
I think the numericals like 1, 2, 3 etc. are not joined but are separate. The reason is that the numericals in Punjabi are not connected with the line above them as is the case with alphabets.
Quote
2) I've noticed there are differences in saroops of guru granth sahib. For e.g. if on one ang the tuk ends with har naam, in another saroop "har naam" may begin on the next ang instead, or har naam might be followed by more words on the ang in another saroop. So when writing a saroop of guru granth sahib ji is it ok to add or move on words at the end/beginning of an ang when it comes to spacing issues?
It does not make a difference if one of more words move on to next page. It is not mandatory to have as many angs as in printed saroops because all handwritten saroops had different amount of angs. Having said that, it is a good idea that the Angs of written saroops now match with the printed Saroops.
Quote
3) Is it ok to have a considerable gap when a new raag starts?
No there should not be a considerable gap between Raags. If you write according to the printed Saroops, then there will be no such problem because it is ensured in the printed Saroops that there is no gap between Raags and Raags in printed Saroops always start on a new Ang. In hand written where Angs ae different than the printed Saroops, the new Raag can start middle of the Ang as opposed to the new ang, as is the case with printed Saroops.
If you follow the printed Saroops in terms of angs and lines on an Ang (there are 19 lines on printed Saroops), then there is a lower chance of making mistakes; otherwise, there is always a major danger of skipping a line. If you skip a line, then you will have to write the whole ang again. It really hurts when you see that the whole Ang that you wrote has been wasted.
Kulbir Singh