Yes, 48 hours ferments at 70F are quite possible, had several myself. Lower gravity worts can ferment fast because the yeast don't have to fight high osmotic pressures.
Yeast can be really sneaky, you probably had an overnight fermentation.
That ring is from the krausen falling and that's normal.
The ale is fine.
Give it another day or two. If the SG is unchanged, move it to the secondary.
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