While these sights are designed to sit on the right side of the rifle, you could potentially flip them around and use them on the left side, they would just fold forward rather than backward.
This product is made in China.
These will provide a 45 degree right hand offset for right handed shooters. If you're specifically looking for left handed offset, you may have to look into something like these Griffin M2's below.
https://www.opticsplanet.com/griffin-armament-m2-micro-modular-sight-deployment-kit.html
With the short rail and integrated iron sights on the UMP 45, this probably wouldn't be ideal.
There is no spec provided by Barska. Using some blue Loctite, it doesn't need to be excessively tight. Torqueing it down to be hand tight should be fine 20-30 inch lbs. should be more than enough.
These are made in China.
There is a side button that releases the sights into the upright position.
Not directly, these require a picatinny rail to mount to, so you would have to add a rail section to your MLOK handguard to mount them.