1: Power use:
The power of a battery in watt-hours can be calculated by multiplying the nominal voltage by the capacity in amp-hours.
3.7V x 0.45AH = 1.66w Watt-Hours. That's 0.166 hours at 10W load.
A 10W lamp would last about ten minutes at best, though quite likely the load current would be too high for such a small cell and it would fail rapidly.
2: Firstly, you _must_ use a proper lithium / lipo charge controller board between the USB power input and the cell or battery!
If you do not, the battery is likely to burst or catch fire.
You can easily get charging PCBs on ebay or amazon that have the proper charge control and battery protection built in.
Or one intended for making a "power bank" may be more suitable, as that should give a fixed 5V out, rather than a voltage that changes as the battery discharges.
Or just use a cheap power bank!