I'm going to throw this out as an extension of the comments on calculators; it's not about dry yeast, but it is something that suggests maybe you're over-concerned about the pitch rate. Bear with me, we'll be back to dry yeast in a bit.
At the boot camp in Asheville I attended two yeast workshops, one put on by Chris White himself (as in the guy who started White Labs). He said he wouldn't make a starter with his yeast, he'd just pitch it in with no starter unless it was a very big beer. Well. You perhaps can imagine my response to this, perplexed as I was.
Fast Forward: my son who is a microbiologist and home brewer was at the same workshop--my wingman you might say--and he says since that workshop, he's just pitched liquid yeast w/ no starter. I've always wanted an active starter going into the wort so it gets going ASAP and can outcompete any nasties in there.
Long story short, made a Kolsch 13 days ago. My son was home and we were talking about this. The Kolsch is a variant of his recipe, and he just pitched the WLP029 in there, no starter. He brought home a growler of that Kolsch, it was great. So, given I was brewing about the same thing, I held my breath
and I pitched that White Labs yeast directly, with no starter.
I know, I have lost my HBT membership card and I'm a bad guy.
**********
Here's how this relates to dry yeast, and why I wonder if just pitching one packet wouldn't work: That beer had an OG of 1.055. The yeast was 3 mos old. The yeast calculator at Brewer's Friend suggests this was a gross underpitch.
Well, if it was, I'm doing it again. I fermented that Kolsch at 60 degrees, and kegged it at 10 days. Yeah. I had it about at 7.5psi at 38 degrees, so I force carbed it a bit to bring it to 10-11psi.
That beer is stunningly good. Took it to the homebrew club meeting Wednesday night--at which time that beer was 11 days old--and it was a hit. I asked my son how conditioning affected this beer, and he says he doesn't know--it doesn't last long enough to find out.
So--the calculator at Brewer's Friend suggests 36 percent viability, or 36 billion cells total in the yeast I used. A packet of dried yeast would have 3x that amount. So what this then points to is....I think you could just pitch one sachet of dried yeast, and you'd be ok.
Your choice, but I'd do that. No starter, just pitch it.