No expert (only taken the MXP Bus once, last February) though I'd say it all depends on whether you have time to familiarize yourself with the route on the way out (between outbound flights). If not I would give yourself more than 75 minutes on the way back.
MXP T1 is two main buildings, the airport, and the garage-complex / train station / Sheraton hotel. Based on what we did in Feb 19 - You'll need to get to the far side of the latter building by taking the escalators down to the basement level of the airport, walk 60 yards or so through a little shopping complex (nothing as big as MUC), through the parking complex / public transport area, through a weird sensory exhibit, and out the far side of that building - next to the streetside entrance of the Sheraton. The Bus drops off and collects from two yellow bus shelters.
The signs posting inside T1 wasn't terrible, though no obvious place to go for information. Once you get outside (next to the Sheraton Entrance) - there is little to distinguish the inter-terminal bus stops. The bus then takes a strange route round the back of an industrial estate (that hardly inspires confidence).
Then you arrive at T2..... if Easy Jet did Airports .... a sea of orange and confused travelers. If you have fast track through security, and HBO like you say, you will find it quite straightforward. It's a small terminal (though it does the ikea trick of making you walk through every inch of it).