As pointed out in this thread, you don't need hundreds of boosters every day to rest your team properly. With a bit of work you don't even need to get any, and you can still max out bonuses and play matches with full condition, check what I said some pages before about how to organise your training sessions.
You DON'T need to perform 2 training sessions (or 4) before a match, it's just a suggestion the app gives to you. You can perfectly avoid any training session (but you won't get bonuses then).
The 2% of bonuses decrease / day has been already there since the beginning of the New Training. This has not changed at all.
Regarding crashes, we're investigating them and will be fixed over the upcoming updates.