I live on Islay and can hopefully give some useful advice on your plans.
There are 2 ferry ports on Islay, one at each end of the island. Make sure you check the timetable to see which one the boat arrives at. If you are arriving late you’d be better off coming into Port Ellen as there’s more choice of B&Bs close to the ferry.
Cycling around Islay is easy and the roads are relatively quiet (some are single track).The wind is likely to be the biggest issue.
Depending on which distilleries you want to visit and if you want to do the guided tour/tasting thing bookings may be required. There’s an excellent café at Ardbeg so worth planning on being there when you’re hungry!
If you are going to do justice to all the Islay distilleries (and everything else the island has to offer) I’d plan on being here for at least 3 days.
Your plan of Jura and passenger ferry to Tavayallich sound good in principle and there’s some lovely countryside along the Crinan Canal. But, for the same reasons that Nobeer has suggested on the Ayshire roads, I wouldn’t recommend the A83 from Ardrishaig to Tarbert. There are folk cycling on it from time to time but it is a tight twisty road with a lot of timber lorries and fast traffic. Not many ways to avoid it unless you take a fairly long detour via Kilberry.
You could come off Jura back to Isly and sail out from Port Askaig to Kennacraig, then its only a 5 mile trip back to Tarbert.
I think Ton on here did a similar trip a couple of years ago. He may give you some good advice.
Have fun