355 Auxillary belt (alternator) teniosner bearing replacement?

Try removing the bracket that the bolt sits on.
Remove all tension, take off the aluminum bracket with the 3x 13mm nuts. Part image attached.
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it can be done. I've done it flat on my back, on the floor, under the car.

loosen nut 13 (do not remove it to begin with), totally remove the tensioner bolt from below, then slide the pully to the lowest position, then remove nut 13 & washer. With a combination of pushing the carrier bolt back and sliding the bearing forward you can get it out, no need to remove the aluminium carrier bracket. If you remove nut 13 first the carrier bolt will bind with the bracket, it only really goes to the lowest position if the carrier bolt is parallel with the housing.

I see in your case that the inner race has detached from the bearing, to get the clearance you'll need to get the pully and inner race off in parallel, as if the bearing were intact, if you see what I mean.