That exact same number of snapped bolts happened to mine ages ago.
I ended up getting the part subframes out, small enough to fit in the oven, heated it to over 200 degrees C - with a really big pair of vice grips on the nubbin of the bolt - I tried melting candle wax into the thread, penetrant, everything under the sun and it would not undo.
The issue is the galvanic corrosion creates powder in the thread, you may get a turn or two out of the bolt before it jams solid - leaving one choice, drill them out - or replace with used ones, for speed I went with the latter option, the new bolts (BTW - Febi kit on ebay is good and cheap) are slathered in anti seize and tightened as much as I could dare.
Last time I checked these were pretty cheap at less than £20 a side, suspect it would save a lot of swearing/drilling