Yes, +P is actually a higher pressure so using the lower pressure regular loads may actually extend its life some.
You need to find a gunsmith or firearms instructor
50-350 usd
45 years old
Mid 1960's.
50-1000 USD depending on specifics.
100-450 USD
Sounds like an after market modification.
69-70
Someone modified it.
100-500 USD
Made in 1953. Model Numbers did not come into use unitl @ 1957. Sounds like you have a Chief Special Airweight. Later numbered as a Model 37.
Depending on condition of the gun and whether or not you have the box & accessories, $175-350