If you had some initial good weeks without the metformin it suggests to me that the issue with your spikes and needing to go to the toilet aren't necessarily metformin related. (Though have you changed your ratios after stopping metformin? You might need to do that and/or bolus a little earlier...?? Am not a pump user so can only male wild guesses.) Maybe you've just got something simple such as a urinary tract infection....?
In any case your endocrinologist should be able to advise you on what to do. Personally, I'd want to know the cause of your new symptoms rather than just take a metformin alternative. And make sure they know about your metformin symptoms because there are some rare but serious metformin side effects (eg lactic acidosis). Honestly, I would have gone to the doctor earlier about that smell because it suggests something is not right. (Though I appreciate everything is/was messed up because of COVID).
Metformin is a pretty unique drug so I haven't heard of any equivalents. Mostly it's used by T2s (am guessing you had an initial T2 diagnosis ?). But some of its side effects are treatable eg B12 deficiency?
There's no obvious reason for a T1 to need drugs other than insulin, though I know some do find metformin helpful. Hopefully you can adjust your insulin pump so that it helps you with the spikes.
Good luck.