Is it permissible to act upon the fatwa of one afflicted with سلس ( سلس البول - سلس الريح - سلس المذي ) when in doubt about the emission of gases for a person suffering from irritable bowel syndrome, and is it permissible for him to combine prayers, and is it obligatory for him to go to the restroom before each prayer to ensure he is free of gases?

The obsessive whispers (waswas) have reached a significant level for you, so you must strive to free yourself from them and pay no attention to them.

If you do not know a specific time when the gases stop exiting, then you have the ruling of a person afflicted with incontinence (sahib al-salas). In this case, perform ablution for prayer after the time for it begins, and pray with this ablution the obligatory prayer and whatever supererogatory prayers you wish.

However, if you know, or it is highly probable, that they stop at a specific time when you can perform ablution and pray, then wait until that time comes.

You are not required to go to the toilet before every prayer unless you need to. If you relieve yourself, then promptly get up and do not prolong your stay.

If you perform ablution, do not pay attention to any obsessive whispers, whether concerning washing the limbs, or the thought that something might have exited from you, or anything else.