no, it won't fit
you need a different MC for ke10/20 because they have a different bolt pattern on the firewall than ke30
the big upgrade for ke30/55/70 is the pajero MC like fook's running, but i think that would be far too big for ke70 calipers
factory ke30 and ke70 master cylinders are the same size, are they not? so in reality, you've just mirrored a ke70 setup with a ke30 booster. i believe the boosters are smaller on the earlier cars (10s and 20s do not have boosters at all, they're not even dual circuit! that's the only reason you'd put an early galant booster on a 10/20 anyway)
not being able to lock your brakes is a good thing. step on the anchors properly in a brand new corolla with decent brakes and you'll be pretty hard pressed to lock anything up. locking up is the worst form of braking you can have, the idea is to get rid of it
have your lines pressure bled, but i reckon you'll get used to it in time. i thought the same thing when i changed from jap calipers to girlock calipers on my ke25, but after doing a few experiments and actually testing the brakes from known braking landmarks i had before, the car actually did stop alot better, despite the fact the pedal felt different
pads may also have something to do with this. hassle teddy to get a wheel off his ke70 and tell you what pads are in it, it stops better than any stock-brake corolla i have ever driven in my life!
your rubber lines may also be a bit on the dodgy side. you can get adr-approved braided lines which would likely improve the situation