No an ap 225 will not support 60-80 clients with 300Mbs of throughput for each client. They might maintain a connect rate of 300Mbs but I don't see getting this kind of throughput.
There are to many unknow variables in your question. just to name a few variables:
Just having one user who far form the ap could cause slow speeds.
Are you limiting users to 5Ghz?
Are all of the users devices capable of 300mbs?
I had a big event at one of my clients sites. We had IAP-225 installed. We didn’t look at the speeds they were getting but each ap handled 100-125 users without issue. No one complained about the speeds they received but I doubt their applications were very bandwidth intensive.