I’m T1D for more than 60 years, on a Tandem pump with Control IQ. Until lunchtime today everything DM-wise was OK. Ate a small normal lunch with the regular lunch bolus. In the last 5 hours my BG has gone from 130 to 330 for no known reason. Now i want get down with a shot of insulin with a pen. My question–if you were me, how many units? Control IQ has been dumping in insulin all afternoon and now because of IOB suggests 0.2 units. The other end of the scale assumes that because of a blockage, kink, air, etc. nothing has reached my body and I need 1.5 U. to get the BG down to 110. A compromise to get the BG down to around 180 would be 1.0 U. What would you do?
You could start with 1U
I would change your infusion set as a precaution.
(Edited out sick day rules)
What I would do is not relevant since this is your body you are going to be injecting. I have no idea how your body reacts to insulin, but hopefully you do.
You don’t mention what your Insulin Sensitivity Factor (aka Correction Factor) is, but you should know it since it is one of the settings that needed to be entered into your pump for it to work.
If it were me, I’d find my current Blood Glucose (BG), subtract the BG I want to reach and then divide the difference by my Correction Factor to get an idea what amount of insulin to bolus as a correction. No? 
Before injecting I’d also take a look at how much Insulin On Board (IOB) the pump thought I still had. Whether or not I lowered the correction bolus amount would depend on how likely I thought it was that the insulin the pump delivered is ever going to effect or whether I thought my infusion site was bad and needed to be changed.
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This feels a little like a homework question with a bunch of confuzzling numbers but lacking the one number (correction factor) we would need to make a quantitative calculation.
My insulin sensitivity must be much less than yours because all of the 0.2-1.5U possibilities you mention would be way way too little for me.
All I can add is that with bg at 330 and rising for no known reason I’d be firmly in “rage bolus”.
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This happens to me when my site stops absorbing. I think change ur site
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I’ve experienced this a lot lately with tandem sites. I’m considering switching site brands with them to an angular tubing.
Hopefully you have already resolved. But I would first do a bg check rather than rely on cgm bg. Then do correction by injection, and test frequently if cgm is far off.
As you suggested, the pump iob may or may not be accurate, so have quick glucose available.
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I find that there is no way I can rely on IOB information since the pump adds and subtracts insulin and, therefore, the different segments of insulin last different times. There were occasions where I thought there was a lot of IOB and manually corrected a certain amount just to find the IOB dropped down to almost nothing within seconds, way too soon to be a result of any insulin I injected. I do not rely on any information about IOB for my manual corrections. Very frustrating.