Is there any information to back this? Are full node operators actually in their thousands? I have always has the fear that the number of people running full node is reducing drastically.
Roughly 16K, at least according to BitNodes though there isn't an accurate methodology to prove this; their crawler sends getaddr to nodes to get a list of IPs which are running a full node and the realtime number can vary drastically. Anyhow, the number shouldn't matter but the geographical distribution is by far more important.
A vast majority of full nodes are Bitcoin Core and for a good reason as well. They are generally well tested and each commit is vetted fairly rigorously and the likelihood of a severe bug or an exploit is unlikely. Though that has happened in the past, most of it are not as severe or easy to execute as the development matures.