Here are some attacks which are affected by the number of nodes and/or miners and/or hashrate:
Attacker: Miners
Attack: Double spending. A miner can spend bitcoins on a product or service, then produce a block which invalidates the spend
Probability of success: 100% when the hash rate of the attacker exceeds the hash rate of the rest of the network
Severity: Number of bitcoins controlled by the attacker * number of attacks performed
The actual severity can be much greater. There can be a run on the coin affecting all HODLers.
You apparently fail to grasp the wealth effect (i.e. that the mcap != amount of capital invested) is mostly built on CONFIDENCE.
Attacker: Miners
Attack: Denial of service. A miner can engage in selective censorship of transactions
Probability of success: 100% when the hash rate of the attacker exceeds the hash rate of the rest of the network
Severity: % success rate of censor identifying transactions they wish to block * value of the blocked transactions
Again you fail to account for out-of-band entropy. The ability to censor key transactions (even if a minute, undetectable %) could lead to immense power-structures, i.e. you threaten to censor the wealth of someone you need to coerce on major political outcome, e.g. a speaker of the house.
Attacker: Nodes
Attack: Double spending. An attacker can defraud a target who is using an SPV wallet by providing them with invalid block headers which allow the attacker to pay the target with a transaction which references non-existant inputs
Probability of success: 0% unless the attacker can prevent the target from communicating with any honest nodes
Severity: Number of bitcoins controlled by the attacker * number of attacks performed
Yes Sybil attacks are another vector and there are lot more cases of attacks that you have not enumerated.