Hi mummy,
Yes the tingling sensation is probably letdown reflex. It should be fine if it's only slightly painful.
130-150ml every 3 hours is not too little, I'd say it's normal. I get about the same amount. However try not to go so long without pumping - I'd say 5 hours max if you'd like to keep the supply up.
Please don't feel guilty if you're really tired and want to give up. Most importantly you should feel strong and be there for the baby. I feel exclusive pumping is much harder and more tiring than direct latching, so if direct latching is really not an option then just go for formula. Nutrient wise there shouldn't be a big difference between breastmilk and formula.