This is what I would do, as that's what you asked. I'm not saying it's what you or anyone else should do as that's too personal to the individual/couple imo.
My experience this pregnancy was that I was in a similar position to you. Good scan, called back after bloods as I was high risk. I'm 40, so similar age as well.
I had a couple of days after getting the letter to think about what I wanted and to discuss it with dh. We didn't get the risk level in the letter. We agreed that 1:100 or better felt like low risk in practice to us. In fact, we agreed after thinking about it that better than 1:50 was a risk we could live with. We took a lot of time to think about what these numbers actually meant, tried to think about situations where that number of people would be gathered together, what that would look like. It was hard, I don't think human brains are really geared up to quantify risk in a meaningful way.
Anyway, I went to the appointment and I didn't feel too bad about it as I'd come to terms with what the NHS considered high risk and what dh & I considered high risk, and I was sure that we'd be ok. Our result was 1:27 so that was a blow. I still swithered a bit about the idea of amnio - it was swapping one risk for another - but I felt that I couldn't go through the pregnancy without knowing, even though our risk still meant there was an over 94% chance all would be fine.
I had the amnio at 17 weeks. I got the initial results back in just over 24 hours which were clear. I got the full results back about 10 days later, also clear. I'm now 38 weeks.
I wish you well whatever you decide. I personally feel you are low risk and I wouldn't have gone ahead with amnio with your results - your age will also influence the figures. The fetal medicine midwife said that even at 1:27 my blood results weren't that bad and we probably wouldn't have been there if I'd been younger. But, there are no guarantees (not with 1:2, not with 1:27, not with 1:140, not with 1:20000) and only you know what level of risk you can live with.
Fingers crossed for a happy, healthy pregnancy x