If the emission rate is fixed at 157,788 per year, then the inflation will be almost 0 after 20 years. But the paragraph above also mentioned less than 1% a year. I thought that inflation figure is fixed. So annual emission will increase although the rate is kept below 1%.
No, after 20 years the inflation rate won't change much at all. At 1% it would hypothetically take roughly 70 years to double the money supply thus reducing inflation in half. In fact it will take longer (because the percentage rate is decreasing each year).
The reduction in the rate of inflation is extremely slow and will at some point likely be exactly offset by the rate of lost coins, resulting in perpetual mining rewards but a real money supply that is effectively fixed. It sounds like a contradiction but it isn't. I describe this more precisely and estimate a possible ending money supply for Monero at 31 million
here.
Monero is using doesn't suffer from the Tragedy of commons to the same degree as Bitcoin does
Correct, but to be fair Bitcoin also doesn't suffer the most severe form of it for 100+ years until the block subsidy run out entirely.