Sill plate on an 8 inch wide cinder block wall

The anchor bolts need to go well into the block, preferably at least 8" in. You should place the anchor bolts in the head joints of the 4" solid run. No need to drill holes in the solid block. Worst case cut the solid block where you need to and set the bolt in the joint created in cut block. They should coincide in a hollow place in the rows of block below often enough to work in a bolt about every 4' maybe slightly more if need be depending on your seismic area. Masonry supply houses carry anchor bolts 16" or 24" long. In my opinion, you should use a minimum of 16", again, depending on your seismic area. There are other types of clips that will do the same as a anchor bolt.

You need to set up a temporary wall under the ends of the ceiling joists of the garage, bearing onto the floor of the garage. Since the section needed is so short, you will only need 5 or 6 2X4s or 2X6s to hold the ceiling and lift the wall for the short time while you replace the bottom plate. If you need 10 ft studs to hold everything up, cut 2 of them in half to double up as top and bottom plates, then use the other 3 to use as studs cut 1/4 longer than needed for a snug fit to lift the existing a little. Get one stud jammed in, set another and with either a hydraulic jack, or by "bowing" them in, as in pushing in the middle of the stud to bow it so it in essence gets shorter between the 2 points until you release it, which will lift the wall a little. work all the studs together one at a time, one will help the other. Or 2 bottle jacks can do it all too, if you have 2 handy. 7 ton, maybe even 2 1/2 ton would work too. That corner, if there is no more than a roof over the garage, is pretty easy to lift up. You wont need much, an 1/8" will do.

This is all on the premise that the loft is contained under the roof with no 2 story bump out to house it, that the roof rafters bear on the top plate of the same wall that has the destroyed bottom plate.