"8. Rewards for the Colosseum decreased in number. (but Colosseum is now more frequent)"
Strongly decreased. It used to be 2-6 items in a chest, now there is 1 for each. Okay, I will use them more carefully.
"9. The number of points for Colosseum rewards has changed. The first ones became much cheaper, the final ones became more expensive. The total number of points to get all awards has increased, but almost entirely at the expense of the last 2-3 awards."
Colosseum 18 (for the crystals) went up from 20.000 to 45.000, while the points you can earn with one fight decreased to around one third (1200-1500 --> 465-510). Getting the crystals with the old setup was tedious, but mostly fair. Now you have to win at least 90 times to get them, not counting that you can't play so many times against to the strongest opponent, because with the recent event sets a lot of them stay up with a full epic deck charged at the 1st turn.
I have almost every cards, missing only 1 set + 4 mythic. Without loosing any fights, I used to finish all Colosseums with 70-80 fights in about 6 hours (of course it's harder and slower if you lost and reset your bonus, or have less cards). Now to win the 18th alone needs more than that. I don't think it's feasible.
Probably it's about time to find a new hobby.