Is it permissible to remove the niqab due to shortness of breath and chest pain, along with not being convinced by it and being content with the lawful hijab?

Scholars have differed regarding the ruling on covering the face, and the most preponderant opinion is that it is obligatory. Disagreement with the obligation is acceptable if it is based on evidence for a female student of knowledge, or the emulation of a trustworthy scholar. Otherwise, you have learned that the most preponderant opinion is that it is obligatory. As for difficulty in breathing due to the niqab, it may disappear with habituation to it. It is not necessary to cover the face with a niqab; any covering is sufficient. It is not permissible to uncover the face according to the opinion of obligation, unless harm is unavoidable when covering it. In that case, you must stay at home and only go out when absolutely necessary.