In October, I need to get from Turin (near Porta Susa) to MXP for a flight to LGW. I found mention of 2 bus services, Flibco and Autostradale/ Arriva, but they both have awful reviews with stories of buses leaving 1 hour late, getting turned away despite advance purchase tickets, etc. I don't have a big time margin. Would I be better off taking a train to Milan and getting to MXP from there? Any thoughts or advice much appreciated.

Edited to also ask: Do I really need to be at MXP 3 hours ahead for a Wednesday late afternoon/early evening flight in late October?