Google Tag Manager (GTM), Google Analytics and Google Optimize - configuration issues

I've got two "bugs" I need help with - both relating to Google Tag Manager and Google products. Both feel like they should be a 5 minute job for the person with the right skills - I am not that person and have spent too long looking!

1) Earlier this year our website bounce rate halved - then it dropped a second time - until this point we believed it to be accurate - at least it looked credible. It has now been at 2% for several months. We have a decent quality website and offer good customer service but 2% is not realistic. Suspect the GA tag might be firing twice or something silly but can't get to bottom of it. We did not make any changes in GTM or the site during the period the drops occurred.

2) I am trying to implement Google Optimize to do some basic on-site A/B testing. The Optimize tag is in GTM. It looks fine. I can't seem to get the Optimize tag to fire. It seems Optimize might need to interact with GA and I'm thinking I haven't set it up correctly.

I have admin access to GTM, GA and Optimize and will invite person to our account.

Website is www.forward2me.com

Thanks,
Lee.