Welcome to Basenotes!
Combining tinctures with oils - just go ahead and combine them - there is no real problem. However I think I would recommend that you start by diluting the essential oils in alcohol to about 10% - that way they are likely to be at a similar strength to your tinctures and also easier to work with.
I'm fascinated by your Oolong tincture - what did you do? Others here have suggested that tea requires a more complex procedure to extract an absolute so if you've had good results with a simple tincture I'd be very interested to hear your method.
Don't worry too much about the ageing process, just go ahead and blend. What usually happens is that you'll find when you've made a successful blend, it will get better over a period of a few weeks. Very rarely you'll find it's not as good after a period of ageing but predicting what will happen is a near to impossible as makes no difference so you'll just have to learn by trial and error. The ageing (in this sense) only starts when you get the ingredients together in the alcohol.
Books: There are several and others will no doubt make different suggestions, but since you are interested in primary extraction of materials and history I'd recommend Septimus Piesse as a place to start. It was published in 1857 by a practicing perfumer and most of it is a good read plus it's cheap. My link will take you to the UK site for Lulu but there will be a US equivalent as the company is based there.
Finally to return to your question about mixing tinctures and oils: some of your tinctures will be relatively high in water because all the water in the plant material ends up in the tincture. That may result in a cloudy mixture when you add essential oils. Another good reason to dilute your oils first in 96% ethanol to reduce the likelihood of that. You won't have a problem with tinctures of dry materials anyway but fresh, fleshy materials like petals and leaves will probably result in a tincture of no more than 80%, which isn't enough to reliably dissolve most essential oils to perfume strength.