If I were you I'd use Interactive Brokers for some or all of you money.
We went through this back in 2008. At the time some futures brokers went bust. We also had some money market funds "break the buck".
What I like about the account at IB is that in terms of cash they keep $250K in the account. Anything above that they transfer to a bank of your choice where you earn interest. No problem using it for investments, they simply transfer it back. It all work seamlessly.
I believe SIPC covers $250K in cash, $500K in assets. It used to be that IB insured up to $5Million I believe I recollect at Lloyds of London. Don't know if they're still doing it or not.
They have a substantial bond offering at IB. I think you could buy anything worldwide. Personally I have a substantial investment in T-Bills which I acquire via IB. Generally I'm holding 6 months to 12 month maturities.
Other products are stocks world wide, futures, forex, gold bullion, bitcoin, etc, all traded at low commissions, and in a univeral account where money is shifted automatically between stocks and futures depending on what you're investing in.
As far as the platform, I can't compare to other offerings. But you can use it with either MAC or PC. I think they offer nearly everything you need, although I probably would say they're platform is mediocre. However, it's useable in my opinion.
I'm a fan.
OldTrader