Would this model leave me vulnerable to being money pumped?

In a certain sense, it does (as long as your 10% beliefs are inaccurate). If you have a lottery A that gives you negative value, I can trade it for a lottery B that is slightly more negative (you 10% chance of getting neither will make you accept this deal). And then itterate.

Or, what about me selling you (in a single transaction) an insurance, good for a hundred trades, that guarantees you against the 10% loss chance?

Generally, inaccurate beliefs leave you open to some sort of arbitrage, even if it's not technically a money pump as described above.