Yearly thousands upon thousands of animals are rescued, £150,000 was raised over 43 “walkies events” in 2016 and much more.
The problem with this sentence is not the use of "much much more", as a phrase, but the fact that you have a list with 2 items and then are trying to add a third item to the list which means "also there are a lot of other things". No matter what phrasing you use, this will be unclear.
It's not really a list, it's 2 things that you're trying to inflate. Because of this, it's not really clear it's a list, and the "and much more" looks like it applies to one single item in the "list", not the list as a whole.
Also, mixing a general achievement "per year" followed by a specific number for a specific year in the same list makes it confusing to read, and so this makes the "and much more" even less clear.
For these reasons, I have chosen a different phrasing to imply "also, there are other things". Among the ____________ allows you to specific to what you are referring.
Among the many achievements of the RSPCA, are the thousands upon thousands of animals rescued each year, and the revenue generated by fundraising events. For example, £150,000 was raised over 43 “walkies events” in 2016.
Note how I have split the general and the year specific examples apart too.