Waiting to see G.I. with my IBS-C which has become progressively worse over the past two years triggered by medications. Linzess gave me horrible pain even at the lowest dose. The laxative that gives me the fewest side effects and works for me is Sennokot. I also found a product by Weber called "the right fiber for IBS" which comes from guar gum and is fodmap approved. It seems to reduce bloating a bit and lessen the Sennokot side effects. You can mix the tasteless and non gritty fine powder into hot or cold beverages. Absolutely tasteless.
I feel badly for you. My severe problems did not start until two and 1/2:years ago 63. (The ibs has been there since my late teens).
I know sennokot should not be used longterm but right now it allows me to get on with my life.
Surgery sounds so drastic and once you take that step there's no going back.