1. its not easy, and it requires knowing what is asur med'oraysa and what is asur medarabanan.
Not too hard. You won't be doing much in the first place. And you could also be machmir and...
but 2 days of shabbos is no fun
I utterly, completely, and categorically disagree. I've done it multiple times and I can't recommend it more.
2. some may view it better to avoid the safek situation altogether
That'll depend on the LOR in question. If your LOR says no than this discussion is moot.
Lol if only it was that simple. I was told to avoid 2 days for reasons such as what do you do about Tefillin on the non-Shabbos day? Etc.
It
is that simple - your LOR will be able to answer all of this for you. Once I got my psak that I need to keep two days, I compiled a list of many, many questions and took it into my Rov. Everything had a simple, black and white answer.
To address your tefillin question, he told me to wear it and daven like a regular weekday.
Shabbos candles was a more interesting issue - you can't light them on Friday afternoon, but at the same time you must light them for Shabbos! So he told me to light yartzeit candles on Thursday afternoon, and "Lekovod Shabbos Kodesh" over them. Then on Friday afternoon, my wife should cover her eyes and make the beracha. This way, no matter when Shabbos really was, we'd be covered
.