You can be a sole proprietor and have employees, so no issue there. It doesn't mean you're a one man band, just that you are the sole owner of the business (no other partners or corporate structures to deal with).
For the CSR the $450 AF sounds scary but it has a $300 travel credit that's pretty easy to use and can offset the AF with expenses you'd usually pay anyway. At that point then it's only $55 more than the CSP and CIP AF's but you get the better redemption rates, GE or TSA PreCheck credit (just 1 every 4 years), and better
travel insurance protections. If any of those things could be useful then it's a good card to pick up as it should justify the $150 price tag then. (It also comes with the Priority Pass lounge access and some status benefits but I don't put a price on those - for me it's not something I'd pay for anyway, others are different) But I would wait until you have some better ideas of using it before deciding. For us it made sense as I use the $300 travel credit on our monthly toll charges. We'd be paying that money anyway so what's the diff if I pay it to EZPass or pay it to Chase first and then get reimbursed? Anything that codes as Travel will get reimbursed unlike the AmEx credits which are for specific charges, and for most, if not all cards, are related to airline charges.